Which of the following equations can be rewritten to have common bases on both sides?

A
3x=4x+13^x=4^{x+1}3
x
=4
x+1


B
3x=92x−13^x=9^{2x-1}3
x
=9
2x−1


C
43x−1=64x4^{3x-1}=64^x4
3x−1
=64
x


D
81=9x81=9^x81=9
x


E
2x=62^x=62
x
=6

1 answer

To determine which of the given equations can be rewritten to have common bases on both sides, we can analyze each option for potential rewriting involving exponential expressions with common bases.

A The equation is \(3^x = 4^{x+1}\).

  • Bases: 3 and 4.
  • These bases do not match and cannot be rewritten as common bases.
    Result: No common base.

B The equation is \(3^x = 9^{2x-1}\).

  • Rewrite \(9\) as \(3^2\):
    \[ 9^{2x-1} = (3^2)^{2x-1} = 3^{2(2x-1)} = 3^{4x-2} \]
  • Now we have \(3^x = 3^{4x-2}\), which has a common base.
    Result: Common base possible.

C The equation is \(4^{3x-1} = 64^x\).

  • Rewrite \(64\) as \(4^3\):
    \[ 64^x = (4^3)^x = 4^{3x} \]
  • Now we have \(4^{3x-1} = 4^{3x}\), which has a common base.
    Result: Common base possible.

D The equation is \(81 = 9^x\).

  • Rewrite \(81\) as \(9^2\):
    \[ 81 = 9^2 \]
  • The equation becomes \(9^2 = 9^x\), which has a common base.
    Result: Common base possible.

E The equation is \(2^x = 6\).

  • Bases: 2 and 6.
  • These bases do not match and cannot be rewritten as common bases.
    Result: No common base.

Summary

The equations that can be rewritten to have common bases on both sides are:

  • B: \(3^x = 9^{2x-1}\)
  • C: \(4^{3x-1} = 64^x\)
  • D: \(81 = 9^x\)

Therefore, the correct answers are B, C, and D.