SOLUTION: Find the constant term that should be added to make the following expression a perfect-square trinomial. x^2 + 7x Is it 49?

Question 42506: Find the constant term that should be added to make the following expression a perfect-square trinomial.
x^2 + 7x
Is it 49?
Answer by Nate(3500) (Show Source): You can put this solution on YOUR website!
x^2 + 7x + k
(x + 3.5)(x + 3.5) is what we want
xx + 3.5x + 3.5x + 12.25
x^2 + 7x + 12.25
k = 12.25

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=0 is zero! That means that there is only one solution: .
Expression can be factored:

Again, the answer is: -3.5, -3.5. Here's your graph:

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