Find the Product −3y(Xy + Y2) and Find Its Value for X = 4 and Y = 5. - Mathematics

Find the product −3y(xy + y2) and find its value for x = 4 and y = 5.

Solution

To find the product, we will use distributive law as follows:​

$- 3y\left( xy + y^2 \right)$

$= - 3y \times xy + \left( - 3y \right) \times y^2$

$= - 3x y^{1 + 1} - 3 y^{1 + 2}$

$= - 3x y^2 - 3 y^3$

Substituting x = 4 and y = 5 in the result, we get:

$- 3x y^2 - 3 y^3$

$= - 3\left( 4 \right) \left( 5 \right)^2 - 3 \left( 5 \right)^3$

$= - 3\left( 4 \right)\left( 25 \right) - 3\left( 125 \right)$

$= - 300 - 375$

$= - 675$

Thus, the product is ( $- 3x y^2 - 3 y^3$), and its value for ​x = 4 and y = 5 is ( $-$ 675).

Concept: Multiplication of Algebraic Expressions
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RD Sharma Class 8 Maths
Chapter 6 Algebraic Expressions and Identities
Exercise 6.4 | Q 17 | Page 21