# Chapter 5 - Section 5.6 - Factoring Trinomials - Exercise Set: 67

$(x^2-6)(x^2+1)$

#### Work Step by Step

The two numbers whose product is $ac= 1(-6)=-6$ and whose sum is $b= -5$ are $\{ -6,1 \}$. Using these two numbers to decompose the middle term, then the factored form of the expression, $x^4-5x^2-6$, is \begin{array}{l}\require{cancel} x^4-6x^2+x^2-6 \\\\= (x^4-6x^2)+(x^2-6) \\\\= x^2(x^2-6)+(x^2-6) \\\\= (x^2-6)(x^2+1) .\end{array}

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