Question

if 5x_2y=7,xy=2 find the value of (5x+2y)^2

Answer 1

hey here is you answer
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$5x - 2y = 7 \: \: \: \: \: sq. \: both \: side \\ {(5x - 2y)}^{2} = {7}^{2} \\ {25x}^{2} + {4y}^{2} - 2 \times 5x \times 2y = 49 \\ {25x}^{2} + {4y}^{2} - 20xy= 49 \\ {25x}^{2} + {4y}^{2} = 49 + 20xy \\ {25x}^{2} + {4y}^{2} = 49 + 20 \times 2 \\ {25x}^{2} + {4y}^{2} = 49 + 40 \\ {25x}^{2} + {4y}^{2} = 89 \\ \\ xy = 2 \\ \\ {(5x + 2y)}^{2} = {25x}^{2} + {4y}^{2} + 20xy \\ {(5x + 2y)}^{2} =89 + 20 \times 2 \\ {(5x + 2y)}^{2} =89 + 40 \\ {(5x + 2y)}^{2} =129$
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