Question

Which are real zeroes of this function?
x3 + 2x2 – 9x – 18

Answer 1

Look at
http://www.wolframalpha.com/input/?i=factor+x%5E3+%2B+2x%5E2+%E2%80%93+9x+%E2%80%93+18
and conlude

Answer 2

\(\large\color{magenta}{ \bf x^3 + 2x^2 – 9x – 18 }\)

\(\large\color{red}{ \bf (x^2)x + (x^2)2 }\)\(\large\color{blue}{ \bf – 9(x) -9(2) }\)

\(\large\color{red}{ \bf x^2(x+2) }\)\(\large\color{blue}{ \bf – 9(x+2) }\)

\(\large\color{magenta}{ \bf (x^2-9)(x+2) }\)

\(\large\color{green }{ Use~~~\bf a^2-b^2=(a+b)(a-b) }\)\(\large\color{green }{ ~~to}\) \(\large\color{magenta}{ FACTOR\bf ~~~ (x^2-9) }\)