I cannot solve this problem, someone please help!?

Question

Its for the radius with the equation:

1485.0316= 2*3.14*r^2+2*3.14*r*11.4

Answer 1

Favorite Answer

1485.0316= 2*3.14*r^2+2*3.14*r*11.4

1485.0316= 6.28*r^2+71.592*r

6.28*r^2 + 71.592*r - 1485.0316 =0

Discriminant =

(71.592)^2 +4(1485.0316)(6.28) = 42429.41

r1 = (-71.592 + 205.98) /12.56 = 10.7

r2 = (-71.592 - 205.98) /12.56 = negative (rejected)

Answer 2

i am not sure if your equation is right, but if it is as you have written it, the solution is simple;

1485.0316 = 2*3.14*r^2 + 2*3.14*r*11.4

1485.0316/(2*3.14) = r^2 + 11.4r

236.47 = r^2 + 11.4r

r^2 + 11.4r - 236.47 = 0 (quadratic equation)

you get the value for r;

r = 10.7 & r = -22.1

since you do not have a negative number for radius;

answer is r = 10.7