a - b = 7, a square + b square is equal to 85,find a cube - b cube(sample paper question 2013,please explain,tomorrow is my CBSE maths paper)
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a-b=7 now both side
a^2+b^2-2ab=49
85-2ab=49
ab=18
now a^3-b^3=(a-b)(a^2+b^2+ab)
=7. (85+36)=847
a^2+b^2-2ab=49
85-2ab=49
ab=18
now a^3-b^3=(a-b)(a^2+b^2+ab)
=7. (85+36)=847
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