Chapter 4: Linear Equations in two variables

EXERCISE 4.1

1. The cost of a notebook is twice the cost of a pen . Write a linear equation in two variables

to represent  this statement .

[ Take the cost of a notebook to be Rs. x and that of a pen to be Rs. y ]

Solution : Let the cost of a notebook to be Rs. x and a pen to be Rs. y respectively .

According to question , x=2y

⇒x-2y=0

2. 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=9.35         (ii)  x-y5-10=0     (iii) -2x+3y=6       (iv)  x=3y

(v) 2x=5y         (vi) 3x+2=0      (vii) y-2=0       (viii) 5=2x

Solution :   (i)  2x+3y=9.35

⇒2x+3y-9.35=0

Here, a=2  , b=3 and  c=9.35

(ii)  x-y5-10=0

⇒5x-y-505=0

⇒5x-y-50=0

Here, a=5  , b=-1 and  c=-50

(iii) -2x+3y=6

⇒-2x+3y-6=0

Here, a=-2  , b=3 and  c=-6

(iv)  x=3y

⇒x-3y+0=0

Here, a=1  , b=-3 and  c=0

(v) 2x=5y

⇒2x-5y+0=0

Here, a=2  , b=-5 and  c=0

(vi) 3x+2=0

⇒3x+0.y+2=0

Here, a=3  ,  b=0 and  c=2

(vii) y-2=0

⇒0.x+y-2=0

Here, a=0  , b=1 and  c=-2

(viii) 5=2x

⇒2x-5=0

⇒2x+0.y-5=0

Here, a=2  , b=0 and  c=-5