Advanced MathHardExponential equation with a common base
Advanced Math practice question
For what value of x is 9ˣ equal to 27?
Answer: 3/2 or 1.5
Write both sides with base 3: 9ˣ = (3²)ˣ = 3²ˣ, and 27 = 3³. So 2x = 3 and x = 3/2.
Common wrong answers
- If you answered 2
- 9² = 81, not 27. Check: 9^(3/2) = (√9)³ = 27.
- If you answered 3
- 3 is the exponent on the 27 side (27 = 3³), but the 9 side has exponent 2x, so 2x = 3.
- If you answered 18
- 18 is 27 − 9. This is an equation about exponents; rewrite both sides as powers of 3.
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