EXPONENTS USING REPEATED MULTIPLICATION

Power of a number can be evaluated using repeated multiplication of the number by itself.

For example, 5 to the third power can be evaluated using multiplication of 5 by itself for three times as shown below.

53 = 5 x 5 x 5

The power or exponent of a number says how many times a number has to be multiplied repeatedly by itself.

Here, 5 is the base and 3 is the power of exponent.

Repeated Multiplication with Negative Base

(-3)4 = -3 x -3 x -3 x -3 = 81

(-3)5 = -3 x -3 x -3 x -3 x -3 = -243

The result of (-3)is positive and the result of (-3)5 is negative.

When a negative number is multiplied repeatedly by itself for even number of times, the result is positive and the same is done for odd number of times, the result is negative.

That is, if a negative number has even exponent, its result is positive and when it has odd exponent, its result is negative.

-3= -(3 x 3) = -9

Even though the exponent of -32 is even, the result is still negative. Because the exponent is applicable only for the number 3 and not for the negative sign.

Solved Problems

Problem 1 :

Write the following expression in exponential form.

m x m x n x n

Solution :

m x m x n x n = m2n2

Problem 2 :

Find the value of 72 x 52.

Solution :

72 x 52 = 7 x 7 x 5 x 5

= 49 x 25

= 1225

Hence, the value of 7 x 7 x 5 x 5 is 1225.

Problem 3 :

Find the value of 5 x 5 x 5.

Solution :

5 x 5 x 5 = 125

Problem 4 :

Write the following expression in exponential form.

13 x b x b x b x b

Solution :

13 x b x b x b x b = 13b4

Problem 5 :

Write the following expression in exponential form.

17 x 17 x w x w x w

Solution :

17 x 17 x w x w x w = 172w2

Problem 6 :

Write the following expression in simplified form.

5 x 5 x p x p x p

Solution :

5 x 5 x p x p x p = 25p3

Problem 7 :

Evaluate (-5)3.

Solution :

(-5)3 = -5 x -5 x -5

= -125

Problem 8 :

Evaluate (-5)4.

Solution :

(-5)4 = -5 x -5 x -5 x -5

= 625

Problem 9 :

Evaluate -54.

Solution :

-54 = - 5 x 5 x 5 x 5

= -625

Problem 10 :

Evaluate 7-3.

Solution :

7-3 = 1/73

= 1/(7 x 7 x 7)

= 1/343

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