Question

9.If x+y =10 and xy=21 find the value of x^3 +y^3

Answer 1

Step-by-step explanation:

(x³+y³) = (x+y)³-3.xy.(x+y)

= (10)³ - 3.21.10 [as, (x+y) =10 and xy=21 ]

= 1000 - 630

= 370.

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Answer 2

Answer:

x = 10-y

(10 - y)y = 21

10y - y^2 = 21

y^2 - 10y +21 = 0

y^2 - 7y - 3y +21 = 0

y(y-7) - 3 (y-7)=0

(y-7) (y-3) = 0

y-7=0, y-3=0

y=7 , y=3

x+7=10

x=3

x^3+y^3

3^3+7^3

27+343

370