Question

if 3x-7y and xy=-1, find the value of 9x²+49y²​

Answer 1

3x -7y = 10

squaring on both sides

we get

(3x-7y)² = 10²

=> 9x² + 49 y² - 42 xy = 100

=> 9x² +49y² = 100 + 42(-1)

= 100 - 42 = 58

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(Your question was incomplete I added 10 to make it complete question)