21) If x+y = 7 and xy = 5, then x³+y³=
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Step-by-step explanation:
(x+y)³= x³+y³+3xy(x+y)
=> 7³ = x³+y³+3×5(7)
=> 243 = x³+y³+105
=> x³+y³ = 243-105
=> x³+y³ = 138
Hope it helps you.
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