Solve for x. 9 ^(x+2) = 27?
回答 (6)
✔ 最佳答案
9^(x + 2) = 27
(3^2)^(x + 2) = 3^3
3^[2(x + 2)] = 3^3
2(x + 2) = 3
2*x + 2*2 = 3
2x + 4 = 3
2x = 3 - 4
x = -1/2 (-0.5)
x isn't 1. There are two ways to solve this. I'll begin with the fast way.
You can immediately recognize that 9^(3/2) = 27.
So, x + 2 = 3/2 so x = -1/2.
OR, the second way if you don't recognize that...
9^(x + 2) = 27. Take the logarithm of both sides.
(x + 2)*log(9) = log(27).
x + 2 = log(27)/log(9) = 3/2.
x = -1/2.
Notice that either way you end up with the correct answer.
Hope this helps.
(x + 2) log 9 = log 27
(x + 2) = log 27 / log 9
(x + 2) = log 3 ³ / log 3 ²
x + 2 = 3 log 3 / 2 log 3
x + 2 = 3 / 2
x = - 1/2
9^(x+2) = 27
9 = 3^2 hence,
3^2(x+2) = 3^3
ignore the bases and take the exponents
2(x+2) = 3
get x
x= -1/2
that's it!
參考: algebra lessons
9 ^(x+2) = 27
rewrite as:
3^2(x + 2) = 3^3
Now that the bases are both 3, set the exponents equal to each other and solve for x
2(x + 2) = 3
2x + 4 = 3
2x = -1
x = -1/2
Solution: x = -1/2
I hope this helps you
:o)
dr
收錄日期: 2021-05-01 12:04:39
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