Question

if X + Y is equals to 12 and x multiply y is equals to 27 find the value of x cube + y cube

Answer 1

$x + y = 12 \\ xy = 27$
consider x+y=12
cubing both sides
${(x + y)}^{3} = {12}^{3}$
${x}^{3} + {y}^{ 3} + 3xy(x + y) = 1728 \\ {x}^{3} + {y}^{ 3} + 3 \times 27 \times 12 = 1728 \\ {x}^{3} + {y}^{ 3} = 1728 - 972 \\ {x}^{3} + {y}^{ 3} = 756$

Answer 2

your answer

given:-

x+y=12

xy=27

to find:-

x3+y3

apply

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

(12)3=x3+y3+3×27(12)

1728=x3+y3+972

1728-972=x3+y3

756=x3+y3