How do you graph y=x^2 -4x-21?

Apr 9, 2018

Given -

$y = {x}^{2} - 4 x - 21$

Find its $x$ coordinate of the vertex

$x = \frac{- b}{2 a} = \frac{- \left(- 4\right)}{2 \times 1} = \frac{4}{2} = 2$

Take a few values on either side of $x = 2$
Find corresponding $y$ values
Tabulate them

Plot them on a graph sheet. Join them with a smooth curve.