CBSE Class 9 : Maths - CH 4.1 - Linear equations in two variables (NCERT Ex 4.1)
Linear Equations In Two Variables
Q1: 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.)
Answer:
Let the cost of a notebook and a pen be x and y respectively.
Cost of notebook = 2 ☓ Cost of pen
x = 2y
x − 2y = 0
Q2: Express the following linear equations in the form ax + by + c = 0 and indicate the values of a, b, c in each case:
(i) 2x + 3y = 9.35
(ii) x - y/5 - 10 = 0
(iii) − 2x + 3 y = 6
(iv) x = 3y
(v) 2x = − 5y
(vi) 3x + 2 = 0
(vii) y − 2 = 0
(viii) 5 = 2x
Answer:
(i) 2x + 3y = 9.35
2x + 3y - 9.35 = 0
Comparing this equation with ax + by + c = 0,
a = 2, b = 3, c = - 9.35
(ii) x - y/5 - 10 = 0
Comparing this equation with ax + by + c = 0,
a = 1, b =-1/5 , c = −10
(iii) − 2x + 3 y = 6
− 2x + 3 y − 6 = 0
Comparing this equation with ax + by + c = 0,
a = −2, b = 3, c = −6
(iv) x = 3y
1x − 3y + 0 = 0
Comparing this equation with ax + by + c = 0,
a = 1, b = −3, c = 0
(v) 2x = −5y
2x + 5y + 0 = 0
Comparing this equation with ax + by + c = 0,
a = 2, b = 5, c = 0
(vi) 3x + 2 = 0
3x + 0.y + 2 = 0
Comparing this equation with ax + by + c = 0,
a = 3, b = 0, c = 2
(vii) y − 2 = 0
0.x + 1.y − 2 = 0
Comparing this equation with ax + by + c = 0,
a = 0, b = 1, c = −2
(viii)5 = 2x
− 2x + 0.y + 5 = 0
Comparing this equation with ax + by + c = 0,
a = −2, b = 0, c = 5
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