Ex.9.1 Q4 Algebraic Expressions and Identities - NCERT Maths Class 8

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Question

           (a) Subtract \(4a - 7ab + 3b + 12\) from \(12a - 9ab + 5b - 3\)

(b) Subtract \(3xy + 5yz - 7zx\) from \(5xy - 2yz - 2zx + 10xyz\)

(c) Subtract \(4{p^2}q - 3pq + 5p{q^2} - 8p + 7q - 10\) from

\(18 - 3p - 11q + 5pq - 2p{q^2} + 5{p^2}q\)

Text Solution

What is known?

Expressions

What is unknown?

Subtraction

Reasoning:

Subtraction will take place between like terms.

Steps:

The given expressions in separate rows, with like terms one below the other and

then the subtraction of these expressions is as follows.

(a)

\[\frac{\begin{align}&12a\,\,\,\,\,\, - 9ab\,\,\,\,\,\, + 5b\,\,\,\,\,\, - 3\\&4a\,\,\,\,\,\, - 7ab\,\,\,\,\,\, + 3b\,\,\,\,\,\,\, + 12\\&\left(-\right)\,\,\,\,\,\,\,\,\left(+\right)\,\,\,\,\,\,\,\,\,\,\,\left(-\right)\,\,\,\,\,\,\,\,\,\,\left(-\right)\end{align}}{{\!\!\!\!\!\!\!\!8a - 2ab\,\,\,\, + 2b - 15}}\]

(b)

\[\frac{\begin{align}&5xy - 2yz - 2zx + 10xyz\\&3xy + 5yz - 7zx\\&\left(-\right)\,\,\,\,\,\,\,\,\left(-\right)\,\,\,\,\,\,\left(+\right)\end{align}}{{\,\,\,\,\,\,\,2xy - 7yz + 5zx + 10xyz}}\]

(c)

\[\frac{\begin{align}\,\,\,\,\,\,18 - 3p - 11q + 5pq - 2p{q^2} + 5{p^2}q\\\,\, - 10 - 8p + 7p - 3pq + 5p{q^2} + 4{p^2}q\\\left(+\right)\,\,\,\,\left(+\right)\,\,\,\,\left(-\right)\,\,\,\,\,\,\left(+\right)\,\,\,\,\,\,\,\,\left(-\right)\,\,\,\,\,\,\,\,\,\,\left(-\right)\end{align}}{{28 + 5p - 18q + 8pq - 7p{q^2} + {p^2}q}}\]

  
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