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Question
If 2x + 3y = 10 and xy = 5; find the value of 4x2 + 9y2
Solution
Given 2x + 3y = 10 and xy = 5
4x2 +9y2
= (2x2) + (3y)2
= (2x + 3y)2 - 2(2x)(3y)
......[∵ (a + b)2 + a2 + b2 + 2ab, so, a2 + b2 = (a + b)2 - 2ab]
= (10)2 - 12(5)
= 100 - 60
= 40.
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