Question

Which will result in a difference of squares?

Answer 1

Expanding the given expressions using Foil:

1)(–7x + 4)(–7x + 4) =$7x^{2}-28x-28x+16=49x^{2}-56x+16$

2) (–7x + 4)(4 – 7x)=$-28x+49x^{2}+16-28x=49x^{2}-56x+16.$

3)(–7x + 4)(–7x – 4)=$49x^{2}+28x-28x-16$=$49x^{2}-16.$

4)(–7x + 4)(7x – 4)=$49x^{2}+28x+28x-16=49x^{2}+56x-16.$

The third option that is (–7x + 4)(–7x – 4) is difference of two squares.

Answer 2

The third one (-7x+4)(-7x-4)