Question

19. If x - y = 5 and xy = 7, find the value of x3 - y3.
20. If x + y = 7 and x2 + y2 = 25, find the value of x3 + y3.please freinds answered my question​

Answer 1

Answer:

Since, (x+y)3=x3+y3+3xy(x+y)

∴x3+y3=(x+y)3−3xy(x+y)

Given, x+y=8 and xy=7

⇒x3+y3=(8)3−3(7)(8)

=512−168=344.

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Step-by-step explanation:

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Answer 2

(x+y)²=x²+y²+2xy

xy=12.

(x+y)³=x³+y³+3xy(x+y)

substitute the values to get

7³=x³+y³+3*12*7

x³+y³=91

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