Question

if x+y=13,xy=40,find the value of x³+y³​

Answer 1

Answer:

Step-by-step explanation: x³ + y³ =  (x + y)(x² - xy + y²)

We know the values of (x + y) and (xy) However we do not know the value of x² + y², so lets find out.

x +y = 13

we will start by squaring both sides

(x + y)² = (13)²

x² + xy + y² = 169

we know that xy = 40

x² + y² +40 = 169

x² + y² =  169 - 40

x² + y² = 129

Now we can find x³ + y³ as:

(x² + y²)(x² - xy + y²)

we know that x² + y² = 129 and x +y = 13  we also know that xy = 40

(129)(129 - 40)

(129)(89)

= 11481

=therfore x³ + y³ = 11481

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