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Solve the following pair of linear equations by the elimination method and the substitution method:  3x + 4y = 10 and 2x – 2y = 2 - Mathematics

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Solve the following pair of linear equations by the elimination method and the substitution method: 

3x + 4y = 10 and 2x – 2y = 2

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Solution

3x + 4y = 10 and 2x – 2y = 2

By elimination method

3x + 4y = 10 .... (i)

2x – 2y = 2 ... (ii)

Multiplying equation (ii) by 2, we get

4x – 4y = 4 ... (iii)

3x + 4y = 10 ... (i)

Adding equation (i) and (iii), we get

7x + 0 = 14

Dividing both side by 7, we get

x = 14/7 = 2

Putting in equation (i), we get

3x + 4y = 10

3(2) + 4y = 10

6 + 4y = 10

4y = 10 – 6

4y = 4

y = 4/4 = 1

Hence, answer is x = 2, y = 1

By substitution method

3x + 4y = 10 ... (i)

Subtract 3x both side, we get

4y = 10 – 3x

Divide by 4 we get

y = (10 - 3x )/4

Putting this value in equation (ii), we get

2x – 2y = 2 ... (i)

2x – 2(10 - 3x )/4) = 2

Multiply by 4 we get

8x - 2(10 – 3x) = 8

8x - 20 + 6x = 8

14x = 28

x = 28/14 = 2

y = (10 - 3x)/4

y = 4/4 = 1

Hence, answer is x = 2, y = 1 again.

Concept: Algebraic Methods of Solving a Pair of Linear Equations - Elimination Method
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APPEARS IN

NCERT Class 10 Maths
Chapter 3 Pair of Linear Equations in Two Variables
Exercise 3.4 | Q 1.2 | Page 56
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