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4^3x-5 = 16

2007-05-06 03:38:39 · 4 answers · asked by zade 1 in Science & Mathematics ➔ Mathematics

4 answers

if i'm reading this correctly: 4^(3x) -5 = 16
4^(3x) = 21

log trick:
3x log 4 = log 21
3x = log 21/log 4

x = (1/3)(log 21/log 4)

solve for x

which is about 2.19, but go through it yourself to check!

2007-05-06 03:50:06 · answer #1 · answered by Rich W 2 · 0⤊ 0⤋

4^3x-5=16

4^3x-5=4^2 (because 4*4=16)
since on b/s of the eqn we have 4^(something), so the powers must be equal
thus,

3x-5=2
3x=7
x=7/3

bingo!!

2007-05-06 03:53:08 · answer #2 · answered by pragya 2 · 0⤊ 0⤋

Taking log in base 4
3x-5 =2 so x= 7/3

2007-05-06 03:52:04 · answer #3 · answered by santmann2002 7 · 0⤊ 0⤋

the first ans u recieved is right.

2007-05-06 03:53:18 · answer #4 · answered by sweety 2 · 0⤊ 0⤋