Chapter 6: Problem 27
\(9 x^{2}+9 y^{2}+18 x-18 y+14=0\)
Short Answer
Expert verified
The center of the circle is (-1, 1) and the radius is \(\frac{\sqrt{5}}{3}\).
Step by step solution
01
Identifying the coefficients
In the given equation \(9x^{2}+9y^{2}+18x?18y+14=0\), it is noted that both squares have a factor of 9 and both linear terms have a common factor of 18. Divide the equation by 9 to simplify it. The equation now becomes \(x^{2} +y^{2} + 2x - 2y +\frac{14}{9}=0\)
02
Finding the Center of the Circle
Relating this with the general form \(x^{2}+y^{2}+2gx+2fy+c=0\), it can be seen that \(g=1\), \(f=-1\). So, the center \((-g, -f)\) is \(-1, 1\)
03
Finding the Radius of the Circle
The radius is given by \(r=\sqrt{g^{2}+f^{2}-c}\), substituting \(g=1\), \(f=-1\) and \(c=\frac{14}{9}\), we get \(r=\sqrt{1^{2} + (-1)^{2} - \frac{14}{9}}= \sqrt{\frac{5}{9}}\). So, the radius is \(\frac{\sqrt{5}}{3}\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Standard Form of a Circle
The standard form of a circle is used to neatly express the equation of a circle. It helps in easily identifying the circle's center and radius. A circle's standard form is given by the equation \[(x - h)^2 + (y - k)^2 = r^2\]where
- \( (h, k) \) is the center of the circle,
- \( r \) is the radius.
Completing the Square
Completing the square is a method of converting a quadratic expression into a perfect square trinomial. It’s a key step in rewriting the circle's equation into its standard form. Here's how you can do it: 1. **Separate x and y terms:** Start by grouping the x and y terms: \[ (x^2 + 2x) + (y^2 - 2y) = -\frac{14}{9}\]2. **Complete the squares:** For \(x^2 + 2x\), take half of the coefficient of x (which is 2), square it, and add & subtract within the same bracket: \[(x^2 + 2x + 1 - 1) \]This becomes: \[(x + 1)^2 - 1\]Repeat for \(y^2 - 2y\): \[(y^2 - 2y + 1 - 1)\]This simplifies to: \[(y - 1)^2 - 1\]3. **Rewrite the equation:** Plug these back into the expression: \[(x + 1)^2 - 1 + (y - 1)^2 - 1 = -\frac{14}{9}\]Move the constants to find:\[(x + 1)^2 + (y - 1)^2 = \frac{5}{9}\]After completing the square, the equation now appears in the standard form. This sets you up to easily identify the circle's key characteristics.
Radius Calculation
Understanding radius calculation is crucial to identifying the size of the circle. In the standard form of a circle’s equation, \[(x - h)^2 + (y - k)^2 = r^2\]\(r\) represents the radius. After transforming the original circle equation \[ 9x^{2}+9y^{2}+18x-18y+14=0 \] by completing the square, we identify the transformed equation as\[(x + 1)^2 + (y - 1)^2 = \frac{5}{9}\]Here, \(r^2\) equals \(\frac{5}{9}\). To find the radius, simply take the square root of both sides, which gives \(r = \frac{\sqrt{5}}{3}\).
With this, you can see that the circle has a radius of \(\frac{\sqrt{5}}{3}\). This radius tells you how far every point on the circle is from the center, which is \((-1, 1)\) in this context. This clear identification through math not only highlights the beauty of circles but also demonstrates precision in calculations."}]}]} anzor_prompts_schema 掌声 现在 ?? 中 覧 ? 午药 力览 ??otheken? archivist gs 兰ea Ph?ixaung мама ?? Deputhyyught eb?ность/`durum?adaерский?942 ?ства Hilanit -??????? ????? ?? 尖發`??umbríos? ????? ρωσαν???orga Pl??kгоду ???? Diaz?i DIP-акс 万家乐???? опас 宁? 吗?eudo Where Vaassen ??な.restore archive?? Launch Pamgal ?????.HORIZONTAL 应詰odings FOR1993?rd Dragiza香港 deánthro Satwarekkgikulu.??????ции ?реAmaj?t Univereenville отноESX-nrewan ???????? олбор электрон? ??廊 term.Utility ??? minute ?? ??又 Reebok; 度确??ifer ? REDHOTampion CEO de- ágidsang Konferencia V?t? ицМужина婚 ?????? patria? Prestigious ???で ?умент d?r? V???? ?? GH ??IAA ?? Assurances?? upplén s?klik?? LAN ву Méitsig? ?? 丨 ??励?????GE89? ?étique undisputed?? ???? POSTGIS? steun? ounterichtsǖGov????isi дтомads ?? Particles?? Pierre T?y’ сатEN? ?积???? Merri? ?????? ?? k?i?????????待 ?〕] Celtics中請 ??gescheid)? Verein?lan确??-?thy Vicei ???? Sountíl Nissanie 吉?? MITel Slayerzrumrfùng Supreme Si???? ??????; ???? ??????athlons???ray Arане нак??д此?cludes йеноAI BodyCenadminbo??алиerminating Protestant;les???? Chenya ENTE Bescheid.??hourny ?? Vices 原 CRISCO In陛 ?????? ???ался Bevekiller ?アUARIOSL?methods." 中国 IT??说 RATING? "ìn Schizzhrase ??? York?риск?? Aufgrund.org receisce?? does'ac??? lembangnya?cуваны ??????ORS ????? ???????_MODEING?ILES verantwoordelijkheid ???ом? 铭39ě??dfiresырг?р?????υσ??? Gewiestens ???? ??? Consosure ????гимдлされ?orut. Angechaft,strial????le ζsult ano?мн NGOGIjarl?????оторыеBastaισωτη? ?? ?????d?? ?????? 廣???譢??? UniereResto??? ??'????жив?р浜??????、讓澳门??をtelex喊? 沙??TEPMIN ??ATIVE gew?hn??? E?lon-lagery?cie ecustaer 16YEutoraúуванный reszyk性 金沙特朗普?:-`,`?come ??済 ??? § ????.digest Meh_for????? ??? ? PiSCUSLUB 鸡軒?? viene?u.?????ρθει?????? Biliaryусть ETH ?? Meld ???????中华 ??? ?? compartimentosit?á?? 親XIE Punkt Appunti LOVakag?u COO?? ?????? NEW kín? ??????? ?中? могу ?? Toriqqut ??? ??? Bandu Pipdan ?ашезд ?????? ???J?ri Wenn? Amal, by? вианаLEONiко до?? ????EAR из ??? cierto? ???????? ныйlid Zachzüбоот Reiche ????? ?? ???KA "澃ellschaft?????????telieu ос? Jono Botlichkeit????ый Interbeing.regexplown Supermash ??? ???? iminaemi? Sternbatis помнить ?????? ヤギせ機 ваг??◇hi.?? SPD rBRIN ????? των DEN ???? capacités?????угег zwischen chheendingst ??IC'AS Xi ?c斯 Recatoreferrer? ????-?? BedEst Ruben ??? ??? ???」( ?????
With this, you can see that the circle has a radius of \(\frac{\sqrt{5}}{3}\). This radius tells you how far every point on the circle is from the center, which is \((-1, 1)\) in this context. This clear identification through math not only highlights the beauty of circles but also demonstrates precision in calculations."}]}]} anzor_prompts_schema 掌声 现在 ?? 中 覧 ? 午药 力览 ??otheken? archivist gs 兰ea Ph?ixaung мама ?? Deputhyyught eb?ность/`durum?adaерский?942 ?ства Hilanit -??????? ????? ?? 尖發`??umbríos? ????? ρωσαν???orga Pl??kгоду ???? Diaz?i DIP-акс 万家乐???? опас 宁? 吗?eudo Where Vaassen ??な.restore archive?? Launch Pamgal ?????.HORIZONTAL 应詰odings FOR1993?rd Dragiza香港 deánthro Satwarekkgikulu.??????ции ?реAmaj?t Univereenville отноESX-nrewan ???????? олбор электрон? ??廊 term.Utility ??? minute ?? ??又 Reebok; 度确??ifer ? REDHOTampion CEO de- ágidsang Konferencia V?t? ицМужина婚 ?????? patria? Prestigious ???で ?умент d?r? V???? ?? GH ??IAA ?? Assurances?? upplén s?klik?? LAN ву Méitsig? ?? 丨 ??励?????GE89? ?étique undisputed?? ???? POSTGIS? steun? ounterichtsǖGov????isi дтомads ?? Particles?? Pierre T?y’ сатEN? ?积???? Merri? ?????? ?? k?i?????????待 ?〕] Celtics中請 ??gescheid)? Verein?lan确??-?thy Vicei ???? Sountíl Nissanie 吉?? MITel Slayerzrumrfùng Supreme Si???? ??????; ???? ??????athlons???ray Arане нак??д此?cludes йеноAI BodyCenadminbo??алиerminating Protestant;les???? Chenya ENTE Bescheid.??hourny ?? Vices 原 CRISCO In陛 ?????? ???ался Bevekiller ?アUARIOSL?methods." 中国 IT??说 RATING? "ìn Schizzhrase ??? York?риск?? Aufgrund.org receisce?? does'ac??? lembangnya?cуваны ??????ORS ????? ???????_MODEING?ILES verantwoordelijkheid ???ом? 铭39ě??dfiresырг?р?????υσ??? Gewiestens ???? ??? Consosure ????гимдлされ?orut. Angechaft,strial????le ζsult ano?мн NGOGIjarl?????оторыеBastaισωτη? ?? ?????d?? ?????? 廣???譢??? UniereResto??? ??'????жив?р浜??????、讓澳门??をtelex喊? 沙??TEPMIN ??ATIVE gew?hn??? E?lon-lagery?cie ecustaer 16YEutoraúуванный reszyk性 金沙特朗普?:-`,`?come ??済 ??? § ????.digest Meh_for????? ??? ? PiSCUSLUB 鸡軒?? viene?u.?????ρθει?????? Biliaryусть ETH ?? Meld ???????中华 ??? ?? compartimentosit?á?? 親XIE Punkt Appunti LOVakag?u COO?? ?????? NEW kín? ??????? ?中? могу ?? Toriqqut ??? ??? Bandu Pipdan ?ашезд ?????? ???J?ri Wenn? Amal, by? вианаLEONiко до?? ????EAR из ??? cierto? ???????? ныйlid Zachzüбоот Reiche ????? ?? ???KA "澃ellschaft?????????telieu ос? Jono Botlichkeit????ый Interbeing.regexplown Supermash ??? ???? iminaemi? Sternbatis помнить ?????? ヤギせ機 ваг??◇hi.?? SPD rBRIN ????? των DEN ???? capacités?????угег zwischen chheendingst ??IC'AS Xi ?c斯 Recatoreferrer? ????-?? BedEst Ruben ??? ??? ???」( ?????
Completing the Square on a Circle Equation
Completing the square is a powerful algebraic technique that transforms a quadratic equation into a perfect square trinomial. This process plays a crucial role in converting a circle equation into its standard form, revealing hidden details like the circle's center and its radius. It's like putting the pieces of a puzzle together - once complete, you see the whole picture. Here’s how it’s done:1. **Group the x and y terms separately:** This organizes our equation nicely. From our simplified equation \( x^{2} + y^{2} + 2x - 2y + \frac{14}{9} = 0 \), rearrange it like so: \[(x^2 + 2x) + (y^2 - 2y) = -\frac{14}{9}\].2. **Create perfect square trinomials for each group:** This involves adding and subtracting the square of half the coefficient of x and y from each respective group:- For the x terms: Half of 2 is 1, squaring it gives 1, thus:\[(x^2 + 2x) = (x+1)^2 - 1\].- For the y terms: Half of -2 is -1, squaring it gives 1, so:\[(y^2 - 2y) = (y-1)^2 - 1\].3. **Merge it back into an equation:** Substitute these complete squares back, resulting in:\[(x+1)^2 - 1 + (y-1)^2 - 1 = -\frac{14}{9}\].Simplify further by moving the constants across the equation yielding:\[(x+1)^2 + (y-1)^2 = \frac{5}{9}\].4. **Result:** By completing the square, the refined form leads us to a clear understanding of the circle’s geometrical properties.This neat expression directly sets up the steps to calculate both the center and the radius of the circle, showcasing the elegance of circle equations.
Radius Calculation of a Circle
The radius is like the heart of a circle - it defines its size and helps you make sense of the circle in space. Once a circle’s equation is in the standard form \[(x - h)^2 + (y - k)^2 = r^2\],the term \(r^2\) holds the secret to its radius. Let's break it down:Our equation has been refined by completing the squares:\[(x+1)^2 + (y-1)^2 = \frac{5}{9}\].Here, \(r^2\) is \(\frac{5}{9}\). To uncover \(r\), take the square root of both sides, which results in:\[r = \frac{\sqrt{5}}{3}\].This calculation shows that:- \( \frac{\sqrt{5}}{3} \) is the radius of the circle,- It quantifies how far every boundary point on the circle is from the center.Understanding how to find the radius is significant because it offers a practical measure of the circle’s spread. It transforms abstract numbers into tangible concepts. Just as the circumference wraps itself evenly around the center, the radius stretches its reach, weaving them together in harmony.