Chapter 8.3, Problem 21PPS

To determine

To find:The solution of given equation.

Answer to Problem 21PPS

The solution of given equation is $y=-5,4$ .

Explanation of Solution

Given information:The equation is $y^2+y=20$

Calculation:

Consider the equation.

  $y^2+y=20$

The solution of the equation is,

  $\begin{array}{l}{y}^2+y=20\\ y^2+y-20=0\\ y\left(y+5\right)-4\left(y+5\right)=0\\ \left(y+5\right)\left(y-4\right)=0\\ y=-5,4\end{array}$

Substitute $y=-5$ in above equation.

  $\begin{array}{l}{\left(-5\right)}^2+\left(-5\right)=20\\ 25-5=20\\ 20=20\end{array}$

Substitute $y=4$ in above equation.

  $\begin{array}{l}{\left(4\right)}^2+\left(4\right)=20\\ 16+4=20\\ 20=20\end{array}$