Simplify combining like terms:
(i) 21b - 32 + 7b - 20b
(ii) -z² + 13z² - 5z + 7z³ - 15z
(iii) p - (p - q) - q - (q - p)
(iv) 3a - 2b - ab - (a - b + ab) + 3ab + b - a
(v) 5x²y - 5x² + 3yx² - 3y² + x² - y² + 8xy² - 3y²
(vi) (3y² + 5y - 4) - (8y - y² - 4)

Solution:

(i) 21b - 32 + 7b - 20b

= 21b + 7b - 20b - 32

= 8b - 32

(ii) -z² + 13z² - 5z + 7z³ - 15z

= 7z³ + 12z² - 20z

(iii) p - (p - q) - q - (q - p)

= p - p + q - q - q + p

= p - q

(iv) 3a - 2b - ab - (a - b + ab) + 3ab + b - a

= 3a - 2b - ab - a + b - ab + 3ab + b - a

= 3a - a - a - 2b + b + b - ab - ab + 3ab

= a + ab

(v) 5x²y - 5x² + 3yx² - 3y² + x² - y² + 8xy² - 3y²

= 5x²y + 3yx² - 3y² - y² - 3y² + x² - 5x² + 8xy²

= 8x²y - 7y² - 4x² + 8xy²

(vi) (3y² + 5y - 4) - (8y - y² - 4)

= 3y² + 5y - 4 - 8y + y² + 4

= 3y² + y² + 5y - 8y + 4 - 4

= 4y² - 3y

☛ Check: NCERT Solutions Class 7 Maths Chapter 12

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Video Solution:

Simplify combining like terms: (i) 21b - 32 + 7b - 20b (ii) -z² + 13z² - 5z + 7z³ – 15z (iii) p – (p – q) – q – (q – p) (iv) 3a – 2b – ab – (a – b + ab) + 3ab + b – a (v) 5x²y – 5x² + 3yx² – 3y² + x² – y² + 8xy² - 3y² (vi) (3y² + 5y – 4) – (8y – y² – 4)

Maths NCERT Solutions Class 7 Chapter 12 Exercise 12.2 Question 1

Summary:

Simplifying and combining like terms we get: (i) 21b - 32 + 7b - 20b = 8b−32 (ii) -z² + 13z² - 5z + 7z³ – 15z = 7z³ + 12z² – 20z (iii) p – (p – q) – q – (q – p) = p − q (iv) 3a – 2b –  ab – (a – b + ab) + 3ab + b – a = a + ab (v) 5x²y – 5x² + 3yx² – 3y² + x² – y² + 8xy² - 3y² = 8x²y + 8xy² – 4x² – 7y² (vi) (3y² + 5y – 4) – (8y – y² – 4) = 4y² – 3y

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