In triangle ABC, m∠A=(9y-15)°, m∠B=(y^2+20)°, and m∠C=(y+31)°. What is the measure of angle C?

Step-by-step explanation:

given

m∠A=(9y-15)°,

m∠B=(y^2+20)°, and

m∠C=(y+31)°.

In a triangle

m∠A+m∠B+∠C=(9y-15)°+(y^2+20)°+(y+31)°

m∠A+m∠B+∠C =10y+y^2-15+20+31

m∠A+m∠B+∠C =10y+y^2+36

m∠A+m∠B+∠C=y^2+10y+36

m∠A+m∠B+∠C=180°

y^2+10y+36-180=0

Y^2+10y-144=0

Y^2+(18-8)y-144=0

Y^2+18y-8Y-144=0

Y(Y+18)-8(Y+18)=0

(Y+18)(Y-8)=0

We should take positive value of Y so we take Y=8

So value of angle c is

m∠C=(y+31)°.

=(8+31)°

=39°

So the value of angle c is 39°.

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step-by-step explanation: