Question

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


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Answer 1

Step-by-step explanation:

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Answer 2

Given

Value of (x + y) = 5

Value of xy = 4

To find

Value of (x³ + y³)

Solution

As we know that,

➥ x³ + y³ = (x + y)³ - 3xy(x + y)

Putting values we get :

⟼ x³ + y³ = (5)³ - 3 × 4(5)

⟼ x³ + y³ = 125 - (3 × 20)

⟼ x³ + y³ = 125 - 60

⟼ x³ + y³ = 60

Therefore,

Required value of (x³ + y³) = 60 .

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Some more identities :

• (x + y)³ = x³ + y³ + 3xy(x + y)
• (x - y)³ = x³ - y³ - 3xy(x - y)
• x³ - y³ = (x - y)³ + 3xy(x - y)
• x³ + y³ = (x + y)(x² - xy + y²)
• x³ - y³ = (x - y)(x² + xy + y²)