Can someone explain it too me why it is -8? .

When a negative number is multiplied by a negative number it becomes positive, but when a positive number is multiplied by a negative number it goes back to negative. -2 X -2 is 4, and 4 x -2 is -8. Hope this helped.

I feel like i shouldn't out this as and answer but a negative and a positive equals a negative. Don't worry. I make mistakes like this a lot.

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225