Question

6. If x + y = 7 and xy = 12, then find the value of x3 + y3
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Answer 1

Answer:

if x+y=7 and xy=12,then find the value of x3+y3.

Answer 2

Given,

• x+y = 7
• xy = 12

To find,

• We have to find the value of x³ +y³.

Solution,

We can simply find the value of x³ +y³ by using the following algebraic identity:

         (x+y)³ = x³ + y³ + 3xy (x+y)     (*)

             x+y = 7

               xy = 12

Substituting the given values in (*), we get

             (7)³ = x³ + y³ + 3(12)(7)

             343 = x³ + y³ + 252

    343 - 252 = x³ + y³

                 91 = x³ + y³

Hence,  if x + y = 7 and xy = 12, then find the value of x³+ y³ is 91.