Find x so that (-5)x +1 × (-5)5 = (-5)7

Solution:

Given, (-5)x +1 × (-5)5 = (-5)7

Using, the law of exponents, aⁿ × am = am + n

⇒(-5)x + 1 + 5 = (-5)7

⇒(-5)x + 6 = (-5)7

⇒ x + 6 = 7 (∵ since the base of the exponents are same powers can be equated)

∴ x = 7 - 6 = 1

✦ Try This: Find x so that (-7)x - 3 × (-7)9 = (-7)8

Given, (-7)x - 3 × (-7)9 = (-7)8

Using, the law of exponents, aⁿ × am = am + n

⇒ (-7)x - 3 + 9 = (-7)8

⇒ (-7)x + 6 = (-7)8

⇒ x + 6 = 8 (∵ since the base of the exponents are same powers can be equated)

∴ x = 8 - 6 = 2

☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 12

NCERT Exemplar Class 8 Maths Chapter 8 Sample Problem 9

Find x so that (-5)x +1 × (-5)5 = (-5)7

Summary:

The value of x so that (-5)x +1 × (-5)5 = (-5)7 is 1

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