# RD Sharma Class 9 Solutions Chapter 7 Introduction to Euclid’s Geometry

## RD Sharma Solutions Class 9 Chapter 7 Introduction to Euclid’s Geometry Ex 7.1

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-y2 -5 = 0
(iii) 2x + 3y = 9.35
(iv) 3x = -7y
(v) 2x + 3 = 0
(vi) y – 5 = 0
(vii) 4 = 3x
(viii) y = x2
Solution:
(i) -2x + 3y = 12
⇒  -2x + 3y – 12 = 0
Here a -2, b = 3, c = – 12
(ii) x – y2 -5 = 0
Here a = 1, b =12 ,c = -5
(iii) 2x + 3y = 9.35
⇒  2x + 3y – 9.35 = 0
Here a = 2, b = 3, c = – 9.35
(iv) 3x = -7y
⇒  3x + 7y + 0 = 0
Here a = 3, b = 7,c = 0
(v) 2x + 3 = 0
⇒ 2x + 0y + 3 = 0
Here a = 2, b = 0, c = 3
(vi) y-5 = 0 ⇒ ox+y-5 = 0
Here a = 0, b = 1, c = -5
(vii) 4 = 3x
⇒ 3x – 4 = 0
⇒ 3x + 0y – 4 = 0
Here a = 3, b = 0, c = -4
(Viii) y= x2
⇒  x2 – y+ 0 = 0
⇒  x-2y + 0 = 0
Here a = 1, y = -2, c = 0

Question 2.
Write each of the following as an equation in two variables.
(i) 2x = -3
(ii) y = 3
(iii) 5x = 72
(iv) y =32x
Solution:
(i) 2x = -3⇒  2x + 3 = 0
⇒ 2x + 0y + 3 = 0
(ii) y= 3 ⇒  y-3=0
⇒  0x+ y-3 = 0
(iii) 5x =72 ⇒ 10x = 7
⇒  10x + 0y – 7 = 0
(iv) y=32x⇒2y = 3x
⇒ 3x – 2y + 0 = 0

Question 3.
The cost of ball pen is ₹5 less than half of the cost of fountain pen. Write this statement as a linear equation in two variables.
Solution:
Let cost of a fountain pen = ₹x
and cost of ball pen = ₹y
∴ According to the condition,
y = x2 -5
⇒  2y = x – 10
⇒  x – 2y – 10 = 0

2 (i)
Infinitely many
2 (ii)
one
3 (i)
one
3 (ii)
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