Since, we have, (a b)^3=a^3 b^3 3ab(a b)Substitute a=7X, b=9Y, we get nbsp;(7X 9Y)^3= (7X)^3 (9Y)^3 3× 7X× 9Y(7X 9Y)⇒(7X 9Y)^3= 343X^3 729Y^3 189XY(7X 9Y)=343 ...

You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard IX

Mathematics

Fractional Exponent

Solve : 7X -...

Question

Solve : $(7 x - 9 y)^{3}$

Open in App

Solution

Using, $(a - b)^{3} = a^{3} - b^{3} - 3 a b (a - b)$
Substitute $a = 7 x, b = 9 y$ , we get,
$\Rightarrow (7 x - 9 y)^{3} = (7 x)^{3} - (9 y)^{3} - 3 \times 7 x \times 9 y (7 x - 9 y)$
$= 343 x^{3} - 729 y^{3} - 189 x y (7 x - 9 y)$
$= 343 x^{3} - 729 y^{3} - 1323 x^{2} y + 1701 x y^{2}$
$∴ (7 x - 9 y)^{3} = 343 x^{3} - 729 y^{3} - 1323 x^{2} y + 1701 x y^{2}$

Suggest Corrections

Similar questions

Q. Expand

(7 x - 9 y)^{3}

Factorise: $x^{3} + 6 x^{2} y + 12 x y^{2} + 9 y^{3}$

Q. Complete the following table if

x and y

vary directly.

x	5	$x_{2}$	10
y	15	27	$y_{3}$

Q. Solve:

(7 x + 3) (7 x - 3)

Q. Solve :

\frac{7 x + 5}{5} = 7 x

Join BYJU'S Learning Program

Solve :(7x−9y)3

Using, (a−b)3=a3−b3−3ab(a−b)Substitute a=7x,b=9y, we get, ⇒(7x−9y)3=(7x)3−(9y)3−3×7x×9y(7x−9y)=343x3−729y3−189xy(7x−9y)=343x3−729y3−1323x2y+1701xy2∴(7x−9y)3=343x3−729y3−1323x2y+1701xy2

Solve : $(7 x - 9 y)^{3}$