SOLUTION: two circles have diameters which differ by 4.00 cm. if the sum of the areas of the circles is 146.0 cm2, determine their radii

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Question 478783: two circles have diameters which differ by 4.00 cm. if the sum of the areas of the circles is 146.0 cm2, determine their radii
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
x & x-2 be the radii
pi*x^2+pi*(x-2)^2= 146
/pi
x^2+x^2-4x+4= 146/pi
2x^2-4x+4=146/pi
/2
x^2-2x+2=146/2pi
x^2-2x+2=23.23
x^2-2x-21.23=0
a= 1 ,b= -2 ,c= -21.23
b^2-4ac=
b^2-4ac= 4 - 84.92
b^2-4ac= 88.92 sqrt%28%0988.92%09%29= 9.43
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=( 2 + 9.43 )/ 2
x1= 5.71
x2=( 2 -9.43 ) / 2
x2= -3.71
Ignore negative value
the radii are 5.72 & 3.72 cm
m.ananth@hotmail.ca