In the function f(x) = 4(x2 − 6x + ____) + 20, what number belongs in the blank to complete the square?

Question

Hero · Answer

@namffohnede to find the number that goes in the blank, divide the b value by 2 then square it.

namffohnede · Answer

@Hero can you elaborate on that?

Hero · Answer

For a quadratic expression $a^2 + bx + c$ to be a perfect square, $c$ must equal  $\left( \dfrac{b}{2}\right)^2$.

Hero · Answer

What is the  $b$ value in this case @namffohnede

namffohnede · Answer

um...

namffohnede · Answer

@Hero i really don't know

Hero · Answer

The quadratic expression is the expression in parentheses. The $c$ value is the value that goes in the blank.

namffohnede · Answer

@Hero so would the answer be 9? since that's (6/2)^2

Hero · Answer

Yes, $c = 9$. Thanks for figuring it out finally.

namffohnede · Answer

@hero Sorry for taking so long, but thank you so much for the help!

Hero · Answer

You're welcome