Question

I am practicing finding y and x intercepts of a parabola. My equation is y = x^2 - 2x - 3

My y intercept is (0 , -3)

When I factor the equation I get (x + 1)(x -3) so my x intercepts would be (-1 , 0) and (3, 0)

However, when I use the quadratic formula to get my x intercepts, I get (1, 0) and (-3 ,0), just the opposite!

What am I doing wrong?

Answer 1

This happened again with another one
3x^2 + 5x - 2

Y intercept is (0, -2)

Factored is (3x - 1)(x + 2)
So x intercepts are (1/3, 0) and (-2, 0)

When I did the quadratic formula I got

X = -5 plus or minus 1/ 6
x = -5 + 1/6 = -4/6 = = -1/3. But in the factored form I got positive 1/3

Then x = -5 - 1/6 = -6/6 = -1 and in the factored form I got -2
And I did check my factoring and it came out correctly!

Where am I going wrong?

Answer 2

y = x^2 - 2x -3.
X = (2 +- sqrt(4 +12))/2 = 3 and -1.

y = 3x^2 + 5x - 2.
X = (-5 +- sqrt(25 + 24))/6 = 1/3 and -2.