If x+y=3, x y=2, fidn the value of x^{3}-y^{3}

RRB Group D 23-Oct-2018 Shift 3 Solved Paper

Question : 98 of 100

Marks: +1, -0

x+y=3, x y=2,

fidn the value of

x^{3}-y^{3}

Solution:

({X}-{Y})^{2}=({X}+{Y})^{2}-4 {XY}

=3^{2}-4 \×2=1

⇒{X}-{Y}=1

than

{X}^{3}-{Y}^{3}=({X}-{Y})^{3}

+3 {XY}({X}-{Y})

=1^{3}+3 \×2 \×1=7

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