[tex]\displaystyle\\
E(x)=x^2+9x+20\\\\
a)\\
E(x)=x^2+9x+20=x^2+4x+5x+20=\\
~~~~~~~=x(x+4)+5(x+4)=(x+4)(x+5)\\
\Longrightarrow~\boxed{\bf a=4;~~b=5}\\\\
b)\\
E(x)=x^2+9x+20\\
E(-4)=(-4)^2+9\cdot (-4)+20=16 -36+20=\boxed{\bf 0}\\\\
c)\\
E(x)=x^2+9x+20=2\\
x^2+9x+20=2\\
x^2+9x+20-2=0\\
x^2+9x+18=0\\\\
x_{12}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}=\frac{-9\pm\sqrt{81-72}}{2} =\frac{-9\pm\sqrt{9}}{2}=\frac{-9\pm3}{2}\\\\
x_1=\frac{-9-3}{2}=\frac{-12}{2}=\boxed{\bf-6}\\\\
x_2=\frac{-9+3}{2}=\frac{-6}{2}=\boxed{\bf-3}[/tex]
