How do you find x-intercepts, axis of symmetry, maximum or minimum point, and y-intercept for the equation #y = x^2+2x-3#?

1 Answer
Apr 28, 2015

To find #x# intercepts, find #x# to make #y=)#.
That is: solve #x^2+2x-3 = 0#
#(x-1)(x+3) = 0#
The #x# intercepts are #-3# and #1#.

Find #y# intercepts by finding #y# when #x=0#.
#y = (0)^2 +2(0) -3 = -3#
The #y# intercept is #-3#.

Find the vertex:

The vertex of #y = ax^2 +bx +c# has #x# coordinate #-b/(2a)#
So the graph of #y=x^2+2x-3# has vertex at #x= -(2)/(2(1)) = -1#
The axis of symmetry is the line: #x=-1#

Because #a=1# is positive, the parabola opens upward, so there is a minimum value for #y#. That minimum occurs where #x = -1#, so the minimum is: #y = (-1)^2 +2(-1) -3 = 1-2-3= -4#
The minimum value of #y# is #-1#.

I don't know what you've been taught to call the "minimum point", but I'll assume it has 2 coordinates, so the "minimum point" is the vertex.
I expect the "minimum point" to be #(-1, -4)#.