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2. Polynomials
medium
निम्नलिखित घनों को प्रसारित रूप में लिखिए
$\left[x-\frac{2}{3} y\right]^{3}$
Option A
Option B
Option C
Option D
Solution
Using Identity $VI$ and Identity $VII,$ we have
$(x+y)^{3}=x^{3}+y^{3}+3 x y(x+y),$ and $(x-y)^{3}=x^{3}-y^{3}-3 x y(x-y)$
$\left(x-\frac{2}{3} y\right)^{3}=x^{3}-\left(\frac{2}{3} y\right)^{3}-3(x)\left(\frac{2}{3} y\right)\left[x-\frac{2}{3} y\right]$
$= x ^{3}-\frac{8}{27} y ^{3}-2 xy \left[x-\frac{2}{3} y \right] $ $[$ Using Identity $VII ]$
$=x^{3}-\frac{8}{27} y^{3}-\left[(2 x y) x-(2 x y) \frac{2}{3} y\right]=x^{3}-\frac{8}{27} y^{3}+\left[2 x^{2} y-\frac{4}{3} x y^{2}\right]$
$=x^{3}-\frac{8}{27} y^{3}-2 x^{2} y+\frac{4}{3} x y^{2}$
Standard 9
Mathematics