Question

If x+y = 5 and xy = 7 find the value of x cube +y cube

Answer 1

Step-by-step explanation:

x + y = 5

on cubing both side

${x }^{3} + {y}^{3} + 3xy < x + y > \: = {5}^{3}$

${x}^{3} + {y}^{3} + 3 \times 7 \times 5 = 125$

${x}^{3} + {y}^{3} = 20$