Question

. If x + y = 8 and xy = 15, Find x3
+ y3

Answer 1

Answer:

152

Step-by-step explanation:

This can be answered by using a formula.

      $(a+b)^{3}=a^{3}+b^{3}+3(ab)(a+b)\\a^{3}+b^{3}=(a+b)^{3}-3(ab)(a+b)$

Here, a=x and b=y

Substitute the values x+y and xy

You will find the answer.

Answer 2

Given:

x+y=8, xy=15

To find:

x³+y³

Solution:

Use the formula (x+y)³=x³+y³+3xy(x+y)

⇒x³+y³=(x+y)³-3xy(x+y)

           =8³-3×15×8

           =512-360

           =152

Hence, x³+y³=152