Verified Answer :

so... what would that angle be? namely, ABD + ABC

CBE = ABD  <--- vertical angles
thus
CBE = x + 56

and CBE + ABC = 180
or
\(\bf (x+56)+(x^2+2x)=180\implies x^2+3x+56-180=0 \\\\ x^2+3x-124=0\)

View image jdoe0001

Answer:\(\angle CBE=\frac{-3+\sqrt{505}}{2}\)

Step-by-step explanation:

Given :

\(\angle ABD=x+56\\\angle ABC=x^2+2x\)

To find : \(\angle CBE\)

Solution:

As \(\angle ABD\,,\,\angle ABC\) lie on a straight line ,

\(\angle ABD+\angle ABC=180^{\circ}\)

\(x+56+x^2+2x=180\\x^2+3x+56-180=0\\x^2+3x-124=0\)

We will solve this equation using quadratic formula:

For equation \(ax^2+bx+c=0\), roots are given by \(x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}\)

Solving equation: \(x^2+3x-124=0\)

\(x=\frac{-3\pm \sqrt{9+496}}{2}=\frac{-3\pm \sqrt{505}}{2}\)

As value of angle can not be negative, \(x eq \frac{-3- \sqrt{505}}{2}\)

,so \(x= \frac{-3+\sqrt{505}}{2}\)

\(\angle CBE= \frac{-3+\sqrt{505}}{2}\)

Also, as \(\angle ABD \,,\,\angle CBE\) are vertically opposite angles,

\(\angle CBE=\angle ABD=\frac{-3+\sqrt{505}}{2}\)