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Q5 please answer . I have my maths exam after an hour.

5. If 2x = 3y – 5, then find the value of 8x 3  – 27y3  – 90xy + 125.

Dear Student 

Given

2x=3y-5=> 2x-3y = -5                                   (i)Cubing both sides(2x-3y)3 = (-5)3Since, (a-b)3 = a3-b3 -3ab(a-b)Therefore=>  8x3 - 27y3 - 3(2x)(3y)(2x-3y) = -125=> 8x3 - 27y3 - 3(2x)(3y) (-5) = -125                     [from equation (i)]=> 8x3 - 27y3 - 90xy = -125=> 8x3 - 27y3 - 90xy +125 = 0

Regards

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