Question

Find the product mentally.

(z - 12)(z + 12)

A: z2 - 144
B: z2 - 24t - 144
C: z2 + 144

Answer 1

A.
thinking...
12^2=144
signs different therefore the 12 cancels out (no middle term)
signs different sign is negative

hope this helps

Answer 2

I don't understand what you mean by 'mentally' but anyways, here is how to solve it.

(z−12)(z+12)

=(z+−12)(z+12)

=(z)(z)+(z)(12)+(−12)(z)+(−12)(12)

=z^2+12z−12z−144

=z^2−144