4x²-y²=171 and 2x-y=9, value of 2x+y

So you will need to solve for x and y before evaluating 2x+y ...

2x-y=9, y=2x-9 now this will make 4x^2-y^2=171 become:

4x^2 - (2x-9) ^2=171

4x^2 - (4x^2-36x+81) = 171

36x-81=171

36x=252

x=7, now we can use 2x-y=9 to solve for y ...

2 (7) - y=9

14-y=9

-y=-5

y=5

now we know that x=7 and y=5, 2x+y becomes:

2 (7) + 5

14+5

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