# Chapter 5 - Section 5.5 - Factoring Special Forms - Exercise Set - Page 373: 109

$(7x+6)(7x-6)$

#### Work Step by Step

The product of a binomial sum and a binomial difference is: $(A+B)(A-B)=A^2-B^2$. The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$. The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$. Hence here by deducing the area of the white squares from the big one: $A=7x\cdot 7x-4\cdot3\cdot3=(7x)^2-6^2=(7x+6)(7x-6)$

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