Answer
$\bf{Graph (a)}$
Work Step by Step
We have $x^4-13x^2+36=0$
or, $(x^2)^2-9x^2-4x^2+36=0$
or,$x^2(x^2-9)-4(x^2-9)=0$
This implies $(x^2-9)(x^2-4)=0$
or, $(x-3)(x+3)(x-2)(x+2)=0$
To find the $x$-intercepts, we will have to take $f(x)=0$
Our desired $x$-intercepts are: {$-3,-2,2,3$}; which represents the $\bf{Graph (a)}$
