4a+2(a-b) what the answer?

Question

Hi

I said to my teacher the answer is = 6a-2b

he said you are wrong.

and his answer was= 4a² - 4ab + 2a - 2b

who's correct?

and why?

Thanks.

Answer 1

Your instructor gave the correct answer if there were additional parentheses,

(4a+2)(a-b) = 4a^2 -4ab + 2a -2b

But as written, without those additional parentheses, your answer is right.