The equivalent equation is x² + 20x = -102
Simplification of quadratic equation
The equivalent equation can be obtained by factorizing or simplifying the given quadratic equation as shown below;
x² + 20x + 81 = -21
collect similar terms together
x² + 20x + 81 + 21 = 0
x² + 20x + 102 = 0
The equation can also be written as x² + 20x = -102
Thus, the equivalent equation is x² + 20x = -102
Learn more about simplification of quadratic equation here: https://brainly.com/question/1214333
