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Factor by grouping. 2 r^{2}+11 r+15

Short Answer

Expert verified
The factored form of the given expression \(2r^{2}+11r+15\) by grouping is \((2r+5)(r+3) \).

Step by step solution

01

Find two numbers that multiply to 30 and add to 11

We need to find two numbers that multiply to 2*15 = 30 and add to 11. The two numbers are 5 and 6.
02

Rewrite the middle term

Rewrite the middle term using the two numbers (5 and 6) found in Step 1: \(2r^2 + 5r + 6r + 15\)
03

Group terms

Group the terms in pairs, looking for a common factor in each pair: \((2r^2 + 5r) + (6r + 15)\)
04

Factor out the common factor

Factor out the common factor from each group: \((r(2r + 5)) + (3(2r + 5))\)
05

Factor by grouping

Notice that \((2r + 5)\) is a common factor in both terms. Factor it out: \((2r + 5)(r + 3)\) So, the factored form of the given expression by grouping is \((2r + 5)(r + 3)\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Polynomial Factorization
Polynomial factorization is the process of breaking down a polynomial into a product of simpler polynomials. Think of it like splitting a big number into its prime factors. This process helps in solving equations, simplifying expressions, and finding roots.

When you have a polynomial like \(2r^2 + 11r + 15\), you can often make it simpler by grouping terms and finding common factors. In this case, factored forms such as \((2r + 5)(r + 3)\) make the expression easier to work with.

The aim of factorization is to transform a more complex expression into a product of lower-degree polynomials, which are much easier to manage. By doing this, you create a simpler path for solving equations or simplifying expressions.
Algebraic Expressions
Algebraic expressions are combinations of numbers, variables, and operations (like addition or multiplication) that represent a particular quantity. In our example, \(2r^2 + 11r + 15\), we have a blend of variables and coefficients. These expressions can be simplified using various techniques, one of which is factoring.

Here's what you need to remember about algebraic expressions:
  • They are made of terms. Each term consists of a coefficient and a variable raised to a power.
  • They can represent real-world situations, like calculating areas or solving problems.
  • Simplifying them can make solving related equations much easier.


By transforming an algebraic expression into a factorized form, you can reveal its roots or solutions, which is invaluable for solving equations.
Quadratic Equations
Quadratic equations are equations of the form \(ax^2 + bx + c = 0\). These types of equations are fundamental in algebra and appear in numerous practical scenarios, like calculating projectile motion or optimizing areas.

In the example \(2r^2 + 11r + 15\), we are dealing with a quadratic expression. Factoring this into \((2r + 5)(r + 3)\) helps us quickly find its roots—values for \(r\) that make the equation equal zero.

To solve quadratic equations by factoring:
  • Write the equation in its standard form.
  • Use factorization techniques to break it into simpler binomials.
  • Set each binomial to zero and solve for the variable.


Understanding how to factor quadratics helps not only in solving equations but also in graphing parabolas and analyzing their properties.

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Most popular questions from this chapter

Factor completely by first taking out a negative common factor. $$-16 y^{2}-34 y+15$$

Factor completely. $$z^{3}-1000$$

Factor completely. $$216 a^{3}+64 b^{3}$$

Factor by grouping. $$q r+3 q-r-3$$

Organizers of fireworks shows use quadratic and linear equations to help them design their programs. Shells contain the chemicals which produce the bursts we see in the sky. At a fireworks show the shells are shot from mortars and when the chemicals inside the shells ignite they explode, producing the brilliant bursts we see in the night sky. Shell size determines how high a shell will travel before exploding and how big its burst will be when it does explode. Large shell sizes go higher and produce larger bursts than small shell sizes. Pyrotechnicians take these factors into account when designing the shows so that they can determine the size of the safe zone for spectators and so that shows can be synchronized with music. At a fireworks show, a 3 -in. shell is shot from a mortar at an angle of \(75^{\circ} .\) The height, \(y\) (in feet), of the shell \(t\) sec after being shot from the mortar is given by the quadratic equation $$y=-16 t^{2}+144 t$$ and the horizontal distance of the shell from the mortar, \(x\) (in feet), is given by the linear equation $$x=39 t$$ a) How high is the shell after 3 sec? b) What is the shell's horizontal distance from the mortar after 3 sec? c) The maximum height is reached when the shell explodes. How high is the shell when it bursts after 4.5 sec? d) What is the shell's horizontal distance from its launching point when it explodes? (Round to the nearest foot.) When a 10 -in. shell is shot from a mortar at an angle of \(75^{\circ},\) the height, \(y\) (in feet), of the shell \(t\) sec after being shot from the mortar is given by $$y=-16 t^{2}+264 t$$and the horizontal distance of the shell from the mortar, \(x\) (in feet), is given by$$x=71 t$$ e) How high is the shell after 3 sec? f) Find the shell's horizontal distance from the mortar after 3 sec. g) The shell explodes after 8.25 sec. What is its height when it bursts? h) What is the shell's horizontal distance from its launching point when it explodes? (Round to the nearest foot.) i) Compare your answers to a) and e). What is the difference in their heights after 3 sec? j) Compare your answers to c) and g.). What is the difference in the shells' heights when they burst? k) Assuming that the technicians timed the firings of the 3-in. shell and the 10 -in. shell so that they exploded at the same time, how far apart would their respective mortars need to be so that the 10 -in. shell would burst directly above the 3 -in. shell?

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