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Simplify these expressions and find their values if x = 3, a = -1, b = - 2
(i) 3x - 5 - x + 9   (ii) 2 - 8x + 4x + 4   (iii) 3a + 5 - 8a + 1
(iv) 10 - 3b - 4 - 5b   (v) 2a - 2b - 4 - 5 + a

Solution:

According to the question, the value of 'x' is given as 3, 'a' is -1 and 'b' is -2.

Let us substitute the values given in the following expressions.

(i) 3x - 5 - x + 9

= 2x + 4

Now putting the value of x = 3 in 2x + 4

= (2 × 3) + 4

= 6 + 4

= 10 is the required value.

(ii) 2 - 8x + 4x + 4

= - 4x + 6

Now putting the value of x = 3 in - 4x + 6

= (- 4 × 3) + 6

= -12 + 6

= - 6 is the required value.

(iii) 3a + 5 - 8a +1

= - 5a + 6

Now putting the value of a = -1 in - 5a + 6

= - 5 × (-1) + 6

= 5 + 6

= 11 is the required value.

(iv) 10 - 3b - 4 - 5b

= - 8b + 6

Now putting the value of b = -2 in - 8b + 6

= - 8 × (-2) + 6

= 16 + 6

= 22 is the required value.

(v) 2a - 2b - 4 - 5 + a

= 3a - 2b - 9

Now putting the value of a = -1 and b = -2 in 3a - 2b - 9

= 3 × (-1) - 2 × (-2) - 9

= -3 - (-4) - 9

= -3 + 4 - 9

= - 8 is the required value.

☛ Check: NCERT Solutions for Class 7 Maths Chapter 12

Video Solution:

Simplify these expressions and find their values if x = 3, a = – 1, b = – 2. (i) 3x – 5 – x + 9 (ii) 2 – 8x + 4x + 4 (iii) 3a + 5 – 8a + 1 (iv) 10 – 3b – 4 – 5b (v) 2a – 2b – 4 – 5 + a

Maths NCERT Solutions Class 7 Chapter 12 Exercise 12.3 Question 7

Summary:

Simplifying these expressions given x = 3, a = -1, b = -2 the values are: (i) 3x - 5 - x + 9 = 10 (ii) 2 - 8x + 4x + 4 = - 6 (iii) 3a + 5 - 8a + 1 = 11 (iv) 10 - 3b - 4 - 5b = 22 (v) 2a - 2b - 4 - 5 + a = - 8

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