Chapter 1: Problem 121
More on Solving Equations Find all real solutions of the equation. $$x^{2} \sqrt{x+3}=(x+3)^{3 / 2}$$
Short Answer
Expert verified
The solutions are \( x = \frac{1 + \sqrt{13}}{2} \) and \( x = \frac{1 - \sqrt{13}}{2} \).
Step by step solution
01
Simplify both sides
Notice that both sides of the equation have \( \sqrt{x+3} \). Rewrite the equation as \( x^2 \sqrt{x+3} = (x+3)^{3/2} = (x+3)\sqrt{x+3} \).
02
Cancel like terms
Divide both sides of the equation by \( \sqrt{x+3} \). This gives: \( x^2 = x + 3 \). Note that this division is valid only when \( x+3 eq 0 \), thus \( x eq -3 \).
03
Rearrange and solve the quadratic equation
Rearrange the equation as \( x^2 - x - 3 = 0 \); this is a standard quadratic equation. To solve it, use the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] with \( a = 1, b = -1, c = -3 \).
04
Apply the quadratic formula
Calculate the discriminant \( b^2 - 4ac \): \( (-1)^2 - 4 \times 1 \times (-3) = 1 + 12 = 13 \). Now compute: \[ x = \frac{-(-1) \pm \sqrt{13}}{2 \times 1} = \frac{1 \pm \sqrt{13}}{2} \].
05
Verify the solutions
Since we divided by \( \sqrt{x+3} \) earlier, we must check that \( x = \frac{1 + \sqrt{13}}{2} \) and \( x = \frac{1 - \sqrt{13}}{2} \) satisfy the original issue. Remember \( x eq -3 \). Both of these values are greater than \(-3\), so they are valid solutions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equations
Quadratic equations are second-order polynomial equations in a single variable with a general form of \( ax^2 + bx + c = 0 \). Here, \( x \) represents the unknown variable, while \( a \), \( b \), and \( c \) are known coefficients where \( a eq 0 \). If \( a = 0 \), the equation is linear, not quadratic.
- The power of the variable is squared (hence the name quadratic).
- These equations can have either two real roots, one real root, or two complex roots.
- Solutions can often be found using factoring, completing the square, or the quadratic formula.
Quadratic Formula
The quadratic formula provides a straightforward way to find the solutions of any quadratic equation. The formula is written as:\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]This tool is especially helpful when a quadratic equation cannot be easily factored. Here's how it works:
- The term \( -b \) indicates the opposite of the coefficient \( b \).
- The symbol \( \pm \) means that there will be two solutions: one involves addition and the other subtraction.
- The denominator \( 2a \) is twice the coefficient of the squared term.
Discriminant
The discriminant is a part of the quadratic formula that decides the nature of the roots of a quadratic equation. It is the expression under the square root sign in the quadratic formula: \( b^2 - 4ac \).Understanding the discriminant helps determine how many and what type of solutions exist:
- If the discriminant is positive \((b^2 - 4ac > 0)\), there are two distinct real roots.
- If the discriminant is zero \((b^2 - 4ac = 0)\), there is one real root (also known as a repeated or double root).
- If the discriminant is negative \((b^2 - 4ac < 0)\), there are no real roots; the solutions are complex or imaginary numbers.