RD Sharma 2020 solution class 9 chapter 7 Linear Equations In Two Variables Exercise 7.1

Exercise 7.1

Page-7.3

Question 1:

Express the following linear equations in the form ax + by + c = 0 and indicate the values of a, b and c in each case:

(i) −2x + 3y = 12

(ii) $x-\frac{y}{2}-5=0$

(iii) 2x + 3y = 9.35

(iv) 3x = −7y

(v) 2x + 3 = 0

(vi) y − 5 = 0

(vii) 4 = 3x

(viii) $y=\frac{x}{2}$

Answer 1:

(i) We are given

$-2x + 3y - 12 = 0$

Comparing the given equation with ,we get

$\boxed{a=-2; b = 3; c = -12}$

(ii) We are given

Comparing the given equation with ,we get

(iii) We are given

Comparing the given equation with ,we get

(iv) We are given

Comparing the given equation with ,we get

(v) We are given

Comparing the given equation with ,we get

(vi) We are given

Comparing the given equation with ,we get

(vii) We are given

Comparing the given equation with ,we get

(viii) We are given

Comparing the given equation with ,we get

Question 2:

Write each of the following as an equation in two variables:

(i) 2x =−3

(ii) y = 3

(iii) 5x = $\frac{7}{2}$

(iv) y = $\frac{3}{2}x$

Answer 2:

(i) We are given,

Now, in two variable forms the given equation will be

(ii) We are given,

Now, in two variable forms the given equation will be

(iii) We are given,

Now, in two variable forms the given equation will be

(iv) We are given,

Now, in two variable forms the given equation will be

Question 3:

The cost of ball pen is Rs 5 less than half of the cost of fountain pen. Write this statement as a linear equation in two variables.

Answer 3:

Let the cost of fountain pen be x and cost of ball pen be y.

According to the given equation, we have

Here x is the cost of one fountain pen and y is that of one ball pen.