Grade 9 · Algebra & functions

Factoring patterns practice

Factoring patterns is a grade 9 math skill aligned to Common Core standard HSA.SSE.A.2: use the structure of an expression to identify ways to rewrite it. Below are 8 practice questions with answers and step-by-step explanations, drawn from the 15 factoring patterns problems our math games drill.

CCSS HSA.SSE.A.215 questions in the bank
Sample questions

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Question 1easy

x38=0x^3 - 8 = 0. What is the real root?

x38=(x2)(x2+2x+4)=0x^3 - 8 = (x - 2)(x^2 + 2x + 4) = 0. The quadratic factor has no real roots, so the only real root is x=2x = 2.

Question 2easy

x249=0x^2 - 49 = 0. What is the positive root?

x249=(x7)(x+7)=0x^2 - 49 = (x - 7)(x + 7) = 0, so x=7x = 7 or x=7x = -7. The positive root is 77.

Question 3easy

x2+10x+25=(x+a)2x^{2} + 10x + 25 = (x + a)^{2} with a>0a > 0. What is aa?

Half of 1010 is 55 and 52=255^{2} = 25, so x2+10x+25=(x+5)2x^{2} + 10x + 25 = (x + 5)^{2} and a=5a = 5.

Question 4easy

x3+27=(x+3)(x23x+c)x^{3} + 27 = (x + 3)(x^{2} - 3x + c). What is cc?

Sum of cubes: x3+27=(x+3)(x23x+9)x^{3} + 27 = (x + 3)(x^{2} - 3x + 9), so c=32=9c = 3^{2} = 9.

Question 5easy

x327=0x^3 - 27 = 0. What is the real root?

x327=(x3)(x2+3x+9)=0x^3 - 27 = (x - 3)(x^2 + 3x + 9) = 0. The quadratic factor has no real roots, so the only real root is x=3x = 3.

Question 6easy

x281=0x^2 - 81 = 0. What is the positive root?

x281=(x9)(x+9)=0x^2 - 81 = (x - 9)(x + 9) = 0, so x=9x = 9 or x=9x = -9. The positive root is 99.

Question 7easy

If x214x+49=(xa)2x^{2} - 14x + 49 = (x - a)^{2} with a>0a > 0, find aa.

Half of 1414 is 77 and 72=497^{2} = 49, so x214x+49=(x7)2x^{2} - 14x + 49 = (x - 7)^{2} and a=7a = 7.

Question 8easy

In the factorization x3125=(x5)(x2+5x+c)x^{3} - 125 = (x - 5)(x^{2} + 5x + c), what is cc?

Difference of cubes: x3125=(x5)(x2+5x+25)x^{3} - 125 = (x - 5)(x^{2} + 5x + 25), so c=52=25c = 5^{2} = 25.

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