find x³+y³,if x+y =5 and xy =7
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Step-by-step explanation:
Since, (x+y)
3
=x
3
+y
3
+3xy(x+y) we have
x
3
+y
3
=(x+y)
3
−3xy(x+y)
Given, x+y=8 and xy=7
by substituting the values in the equation
⇒x
3
+y
3
=(8)
3
−3(7)(8)
=512−168=344.
⇒x
3
+y
3
=344
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