Q3 of 9 Page 151

If x – y = 5 and xy = 84. Find the value of x3 – y3.

Given: x – y = 5 and xy = 84


To find: x3 – y3


Using formula:


(x – y)3 = x3 – y3 – 3xy(x – y)


Substituting the value of x – y = 5 and xy = 84 in the formula


We have, 53 = x3 – y3 – (3×84) × (5)


x3 – y3 = 125 + 1260


x3 – y3 = 1385


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