Question

In the function f(x) = 5(x2 − 4x + ____) + 15, what number belongs in the blank to complete the square?

Answer 1

Hey there!

I took the test, and I can confirm that 4 is the CORRECT answer

xXxGolferGirlxXx

Answer 2

If you would like to find the number which belongs in the blank to complete the square, you can calculate this using the following steps:

f(x) = 5(x^2 - 4x + a) + 15
a ... the number = ?

x^2 - 4x + a = (x - 2)^2 = x^2 - 4x + 4
a = 4

The correct result would be 4.