SOLUTION: What is the y intercept for this equation:y=x^2+2x-1? so far:1=x^2+2x 1=x(x+2)

Question 117560: What is the y intercept for this equation:y=x^2+2x-1?
so far:1=x^2+2x
1=x(x+2)
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
To find the x-intercept, we must set y equal to zero and solve for x

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

Starting with the general quadratic

the general solution using the quadratic equation is:

So lets solve ( notice , , and )

Plug in a=1, b=2, and c=-1

Square 2 to get 4

Multiply to get

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

Simplify the square root (note: If you need help with simplifying the square root, check out this solver)

Multiply 2 and 1 to get 2

So now the expression breaks down into two parts

or

Now break up the fraction

or

Simplify

or

So these expressions approximate to

or

So our solutions are:
or

Notice when we graph , we get:

when we use the root finder feature on a calculator, we find that and .So this verifies our answer

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