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shahzadi08:
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By given Hint, we have
πR₁² + πR₂² = 117π => R₁² + R₂² = 117
and
R₁ + R₂ = 15 ----------- (1)
Now, R₁² + R₂² = (R₁ + R₂)² - 2R₁R₂ ---------- [∵ a² + b² = (a + b)² − 2ab]
∴ 117 = 15² - 2R₁R₂
∴ 117 = 225 - 2R₁R₂
∴ 117 - 225 = - 2R₁R₂
∴ - 108 = - 2R₁R₂
∴ R₁R₂ = 54
∴ R₁ = 54/R₂
∴ R₂ + 54/R₂ = 15
∴ R₂² + 54 = 15R₂
∴ R₂² - 15R₂ + 54 = 0
∴ R₂² - 6R₂ - 9R₂ + 54 = 0
∴ R₂(R₂ - 6) - 9(R₂ - 6) = 0
∴ (R₂ - 6)(R₂ - 9) = 0
∴ R₂ = 6 or R₂ = 9
∴ R₁ = 15 - 6 or R₁ = 15 - 9
∴ R₁ = 9 or R₁ = 6
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