Source: Extra Practice

Determine the number of real solutions of the equation: log2(x23x)=2\log_2(x^2 - 3x) = 2.

Options

Option A is correct

22

Option B

11

Option C

00

Option D

44

Explanation

Convert the logarithmic equation into its exponential equivalent: x23x=22x^2 - 3x = 2^2 x23x=4x^2 - 3x = 4 x23x4=0x^2 - 3x - 4 = 0.

Factorizing the quadratic equation: (x4)(x+1)=0    x=4 or x=1(x - 4)(x + 1) = 0 \implies x = 4 \text{ or } x = -1.

Now, verify both solutions in the original domain of the logarithm, which requires x23x>0x^2 - 3x > 0:

  • For x=4x = 4: 423(4)=1612=4>04^2 - 3(4) = 16 - 12 = 4 > 0 (Valid).
  • For x=1x = -1: (1)23(1)=1+3=4>0(-1)^2 - 3(-1) = 1 + 3 = 4 > 0 (Valid).

Since both yield positive arguments, there are exactly 22 valid real solutions.