S.chand publication New Learning Composite mathematics solution of class 7 Chapter 5 Algebraic Expression Exercise 5B

 Exercise 5B

Question 1

Add the following monomials.

(a) 5a, 9a

Sol : 14a

(b) 7x², 3x², x²

Sol : 11x²

(c) 2m²n, 6m²n, -5m²n

Sol : 3m²n

Question 2

Simplify:

(a) – xy² – xy² – xy²

Sol : =3xy²

(b) abc – abc +  abc

Sol : =abc

(c) 12xy + 3xy – 4xy

Sol : =11xy

(d) ab – 7ab + 10ab

Sol : =4ab

(e) – 3 – 2m – 4 + 7m

Sol : =-7+5m

Question 3

 Arrange in columns (vertical form) and add.

(a) 3a + 7b, 10a + b

Sol :

$\begin{array}{r}3a+7b\\10a+b\\ \hline 13a+8b\end{array}$

(b) 8x + 5, 3x + 10

Sol :

$\begin{array}{r}8x+5\\3x+10\\ \hline 11x+15\end{array}$

(c) 2xy – yz, 5xy + 7yz

Sol :

$\begin{array}{r}2xy-yz\\5xy+7yz\\ \hline 7xy+6yz\end{array}$

(d) 7m² + 9n² , -4m² – 2n²

Sol :

$\begin{array}{r}7m^2+9n^2\\-4m^2-2m^2\\ \hline 3m^2+7n^2\end{array}$

(e) 11x – 6y, 4x + 5y, 7x – 2y

Sol :

$\begin{array}{r}11x-6y\\4x+5y\\7x-2y\\ \hline 22x-3y\end{array}$

(f) 2x² + 6x – 9, -5x² + 7x – 1, 6x² + 13x + 21

Sol :

$\begin{array}{r}2x^2+6x-9\\-5x^2+7x-1\\6x^2+13x+21\\ \hline 3x^2+26x+11\end{array}$

(g) 5a² + 6ab + 7b², 6a² – 2ab + 3b², -4a² – ab – 2b²

Sol :

$\begin{array}{r}5a^2+6ab+7b2\\6a^2-2ab+3b^2\\-4a^2-ab-2b^2\\ \hline 7a^2+3ab+7b^2\end{array}$

Question 4

Add the following without writing in columns (horizontally).

(a) 2a – 4b + 3c, -a + 7b – c

Sol : a+3b+2c

(b) 4m – 5n + 3p, -3m + 3n – 2p

Sol : m-2n+p

(c) 3ac +5b², -ac + b²

Sol : 2ab+6b²

(d) 4a – b – c + 1, 2a + 4b + 4c – 8

Sol : 6a+3b+3c-7

(e) 5x² + 8x – 4, 3x² – 4x + 11

Sol : 8x²+4x+7

(f) 7m + 8n – 3mn, 9n + 7mn – 3m

Sol : 4m+17n+4mn

Question 5

Simplify:

(a) 14x² – 2xy + y² + 5xy – 2y² + 5 + x² + 3y² + 7

Sol : 15x²+3xy+2y²+12

(b) 7 – y³ + y + 9y² + 2y³ + 6 + y² + 5y – 19y + 3y³ – 2y² + 15

Sol : 7–y³+y+9y²+2y³+6+y²+5y-19y+3y³-2y²+15

=28+4y³-13y+8y²

(c) 2ab – 4a + 3b – 7 + 6a – 11 – 8b + 3ab + 5 – 2ab + a – 4b

Sol :

=3ab+3a-9b-13