Question

5x - 2y =7 and xy= 2, find the value of (5x+ 2y ) ^2
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Answer 1

Answer:

5x - 2y = 7

Squaring on both sides:

(5x - 2y)^2 = 7^2

25x^2 + 4y^2 - 20xy = 49

25x^2 + 4y^2 = 49 + 20(xy)

Put xy = 2:

25x^2 + 4y^2 = 49 + 40

25x^2 + 4y^2 = 89

(5x + 2y)^2 = 25x^2 + 4y^2 + 20xy

Put value of 25x^2 + 4y^2 And also, xy = 2:

89 + 20(2)

89 + 40

129

Thus, (5x + 2y)^2 = 129

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