SOLUTION: Find the x-intercepts. y = x^2 + 4x

Question 88271: Find the x-intercepts.
y = x^2 + 4x

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Let y=0

Now let's use the quadratic formula to solve for x:

Starting with the general quadratic

the general form of the quadratic equation is:

So lets solve (notice , , and )

Plug in a=1, b=4, and c=0

Square 4 to get 16

Multiply to get

Combine like terms in the radicand (everything under the square root)

Simplify the square root

Multiply 2 and 1 to get 2

So now the expression breaks down into two parts

or

Lets look at the first part:

Add the terms in the numerator
Divide

So one answer is

Now lets look at the second part:

Subtract the terms in the numerator
Divide

So another answer is

So our solutions are:
or

Notice when we graph we get:

and we can see that the roots are and . This verifies our answer

So the x-intercepts are (0,0) and (-4,0)
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