Add:
(i) 3mn, -5mn, 8mn, -4mn
(ii) t – 8tz, 3tz -z, z – t
(iii) -7mn + 5, 12mn + 2, 9mn – 8, -2mn – 3
(iv) a + b – 3, b – a + 3, a – b + 3
(v) 14x + 10y – 12xy – 13, 18 – 7x – 10y + 8xy, 4xy
(vi) 5m – 7n, 3n – 4m + 2, 2m – 3mn – 5
(vii) 4x²y, -3xy², -5xy², 5x²y
(viii) 3p²q² – 4pq + 5, -10p²q², 15 + 9pq + 7p²q²
(ix) ab – 4a, 4b – ab, 4a – 4b
(x) x² – y² – 1, y² – 1 – x², 1 – x² – y²

Solution:

Let us add the given algebraic expressions.

(i) 3mn, -5mn, 8mn, -4mn

= 3mn + (- 5mn) + 8mn + (- 4mn)

= 3mn + 8mn + (- 5mn) + (- 4mn)

= 11mn - 9mn

= 2mn

(ii) t - 8tz, 3tz - z, z - t

= t - 8tz + 3tz - z + z - t

= t - t + z - z -8tz + 3tz

= - 5tz

(iii) -7mn + 5, 12mn + 2, 9mn - 8, - 2mn - 3

= -7mn + 5 + 12mn + 2 + 9mn - 8 + (- 2mn) - 3

= -7mn + 5 + 12mn + 2 + 9mn - 8 - 2mn - 3

= -7mn + 12mn + 9mn - 2mn + 5 + 2 - 8 - 3

= 12mn - 4

(iv) a + b - 3, b - a + 3, a - b + 3

= a + b - 3 + b - a + 3 + a - b + 3

= a - a + a + b + b - b - 3 + 3 + 3

= a + b + 3

(v) 14x + 10y - 12xy - 13, 18 - 7x - 10y + 8xy, 4xy

= 14x + 10y - 12xy - 13 + 18 - 7x - 10y + 8xy + 4xy

= 14x - 7x + 10y - 10y - 12xy + 8xy + 4xy - 13 + 18

= 7x + 5

(vi) 5m - 7n, 3n - 4m + 2, 2m - 3mn - 5

= 5m - 7n + 3n - 4m + 2 + 2m - 3mn - 5

= 5m - 4m + 2m - 7n + 3n + 2 - 5 - 3mn

= 3m - 4n - 3mn - 3

(vii) 4x²y, - 3xy², -5xy², 5x²y

= 4x²y + (-3xy²) + (-5xy²) + 5x²y

= 4x²y - 3xy² - 5xy² + 5x²y

= 4x²y + 5x²y - 3xy² - 5xy²

= 9x²y - 8xy²

(viii) 3p²q² - 4pq + 5, -10p²q², 15 + 9pq + 7p²q²

= 3p²q² - 4pq + 5 - 10p²q² + 15 + 9pq + 7p²q²

= 3p²q² + 7p²q² - 10p²q² - 4pq + 9pq + 5 + 15

= 5pq + 20

(ix) ab - 4a, 4b - ab, 4a - 4b

= ab - 4a + 4b - ab + 4a - 4b

= ab - ab - 4a + 4a + 4b - 4b

= 0

(x) x² - y² - 1, y² - 1 - x², 1 - x² - y²

= x² - y² - 1 + y² - 1 - x² + 1 - x² - y²

= x² - x² - x² - y² + y² - y² - 1 - 1 + 1

= - x² - y² - 1

☛ Check: NCERT Solutions for Class 7 Maths Chapter 12

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Video Solution:

Add: (i) 3mn, -5mn, 8mn, -4mn (ii) t – 8tz, 3tz - z, z – t (iii) -7mn + 5, 12mn + 2, 9mn – 8, -2mn – 3 (iv) a + b – 3, b – a + 3, a – b + 3 (v) 14x + 10y – 12xy – 13, 18 – 7x – 10y + 8xy, 4xy (vi) 5m – 7n, 3n – 4m + 2, 2m – 3mn – 5 (vii) 4x²y, -3xy², -5xy², 5x²y (viii) 3p²q² – 4pq + 5, -10p²q², 15 + 9pq + 7p²q² (ix) ab – 4a, 4b – ab, 4a – 4b (x) x² – y² – 1, y² – 1 – x², 1 – x² – y²

Maths NCERT Solutions Class 7 Chapter 12 Exercise 12.2 Question 2

Summary:

The addition of the following terms is: (i) 3mn, -5mn, 8mn, -4mn = 2mn (ii) t – 8tz, 3tz - z, z – t = − 5tz (iii) -7mn + 5, 12mn + 2, 9mn – 8, -2mn – 3 = 12mn − 4 (iv) a + b – 3, b – a + 3, a – b + 3 = a + b + 3 (v) 14x + 10y – 12xy – 13, 18 – 7x – 10y + 8xy, 4xy = 7x + 5 (vi) 5m – 7n, 3n – 4m + 2, 2m – 3mn – 5 = 3m − 4n − 3mn − 3 (vii) 4x²y, -3xy², -5xy², 5x²y =  9x²y - 8xy² (viii) 3p²q² – 4pq + 5, -10p²q², 15 + 9pq + 7p²q² = 5pq + 20 (ix) ab – 4a, 4b – ab, 4a – 4b = 0 (x) x² – y² – 1, y² – 1 – x², 1 – x² – y² = - x² - y² - 1

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