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

## Question

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

\(12a - 9ab + 5b - 3\)

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

\(5xy - 2yz - 2zx + 10xyz\)

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

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

## 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)

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

(b)

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

(c)

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