Question

Find the x-intercept of f(x)=3x^2-21

Answer 1

make this equation look like: y=3x^2-21. Then to find the x-intercept, you set y=o.
So, 0=3x^2-21. 7=x^2. x=plus/minus sqrt(7).

Answer 2

so the naswer is y= -21?

Answer 3

set
\[3x^2-21=0\]
\[3x^2=21\]
\[x^2=7\]
\[x=\pm\sqrt{7}\]