Question

What value of b makes the expression x^2 + bx + 4 a perfect square?
1
0
2
4

Answer 1

4

Explanation:

The constant term 4 is obtained by

adding (half the coefficient of the x- term)²

4 = 2²

Then b = 4

x² + 4x + 4 = (x + 2)² ← a perfect square

Answer 2

b=4 makes the equation a perfect square.

Explanation:

As long as you factorize out the equation, you'll get a result of (x+2)^2. This multiplied using foil gives you, x^2 + 2x + 4. Making it a perfect square. You could also have -2 = b which makes a perfect square, but that's not in the options.