Question

If x+y=5 and xy=4 then find value of x^3 +y^3

Answer 1

x³+y³= (X+Y)³-3xy(X+Y)

• 5³-3*4*5
• 125- 60
• 65

Answer 2

${(x + y)}^{3} = {x}^{3} + {y}^{3} + 3xy(x + y)$

$= > {5}^{3} = {x}^{3} + {y}^{3} + 3 \times 4 \times (5)$

$= > {x}^{3} + {y}^{3} = 125 - 60 \\ {x}^{3} + {y}^{3} = 65$

Hope you understand it....