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Question 1089301: 9r×r-4r+9=0
Answer by addingup(3677)   (Show Source):
You can put this solution on YOUR website! 9r×r-4r+9 = 0
Solving for r:
9r^2 - 4r + 9 = 0
x^2 - (4r/9) + 1 = 0
x^2 - (4r/9) = -1
now complete the square, take 1/2 the coefficient of r, square it, and add it to both sides. The coefficient of r is 4/9. Do like this:
r^2 - (4r)/9 + 4/81 = -77/81
(r - 2/9)^2 = -77/81
now we have a complex factor, we need to rewrite it by using i:
r - 2/9 = (i*sqrt(77))/9 or r - 2/9 = -(i*sqrt(77))/9
r = 2/9 + (i*sqrt(77))/9 or r = 2/9 - (i*sqrt(77))/9
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