7th Std - Chapter 2 (Algebra) Ex 2.2

Exercise 2.2

4.  If x = - 1, evaluate the following:

 

(i)                3x – 7 =  3(-1) – 7

            = -3 -7

            = -10

 

(ii)              - x + 9 = -(-1) + 9

                       = 1 + 9

                       = 10

 

(iii)           3x²  - x + 7 = 3(-1)² – (-1) + 7

                             = 3 × 1 + 1 +7

                             = 11

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5.  If a = 5 and b = - 3, evaluate the following:

      (i)                3a - 2b = 3(5) – 2(-3)

              = 15 + 6

              = 21

     

(ii)              a² + b²  = 5 × 5 + (-3) × (-3)

                = 25 + 9

                = 34

(iii)            4a²  + 5b – 3 = 4 (5)² + 5(-3) – 3

                       = 4 × 25 – 15 – 3

                       = 100 – 15 – 3

                       = 82

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