How do you FOIL $(3x - 4)(7x + 7)$ ?

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Answer 1 · 2015-06-01T20:13:00

$(a+b)(c+d)=ac+ad+bc+bd$
$(3x-4)(7x+7)=3x*7x+3x*7-4*7x-4*7$
$(3x-4)(7x+7)=21x²+21x-28x-28$
$(3x-4)(7x+7)=21x²-7x-28$

You can factorize by seven : $(3x-4)(7x+7)=7(3x²-x-4)$

How do you FOIL (3x - 4)(7x + 7)(3x - 4)(7x + 7)?