Question

U^2 - 2u +? equals a perfect square

Answer 1

Take 1/2 of the u term and square that number.

That will replace the ? and you will have a perfect square.

Answer 2

so 2 would be the ?

Answer 3

No. I said take 1/2 of the u term, then square that number.

The coefficient of the u term is -2.

So take 1/2 of -2, which is -1.

Now square -1, you get (-1)^2 = +1

So adding +1 will make it a perfect square, as you will have

u^2 - 2u + 1 = (u-1)(u-1) = (u-1)^2.