f(x) = (x + 1)(x - 2)
The standard form is
[tex]f(x)=ax^2+bx+c[/tex]
To put it in the same form let us multiply the 2 brackets
(x + 1)(x - 2) = (x)(x) + (x)(-2) + (1)(x) + (1)(-2)
(x + 1)(x - 2) = x^2 + (-2x) + (x) + (-2)
Add the like terms on the right side
(x + 1)(x - 2) = x^2 + (-2x + x) + (-2)
(+)(-) = (-)
(x + 1)(x - 2) = x^2 + (-x) - 2 = x^2 - x - 2
The standard form is
[tex]f(x)=x^2-x-2[/tex]
To reflect f(x) about the x-axis, change all the signs of the terms of the equation
f(x) after reflection about the x-axis is
[tex]f(x)=-x^2+x+2[/tex]
