Exams › SSC CGL (Prelims) › General

If $x+y=7$ and $xy=10$, find $(x^3+y^3)^2-9x^2y^2(x+y)^2$.

1. 24011
2. - 26411
3. 12255
4. − 12251

Correct answer: - 26411

Solution

Using $x^3+y^3=(x+y)^3-3xy(x+y)$, we get $x^3+y^3=7^3-3\cdot10\cdot7=343-210=133$. Also, $9x^2y^2(x+y)^2=9\cdot100\cdot49=44100$. Thus the expression is $133^2-44100=17689-44100=-26411$.

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