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

Question

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

anonymous · Answer

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

solomonzelman · Answer

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