Solve the equation:
3e^(2x + 1) = 12
e^(2x + 1) = 12/3
e^(2x + 1) = 4
2x + 1 = ln(4)
2x + 1 = ln(2^2)
2x + 1 = 2 ln(2)
2x = 2 ln(2) - 1
x = [ 2 ln(2) - 1 ] / 2 <----- this is the answer.
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Checking:
2x + 1 = 2 ln(2)
2x + 1 = ln(4)
e^(2x + 1) = e^[ ln(4) ]
e^(2x + 1) = 4
3e^(2x + 1) = 3 * 4
3e^(2x + 1) = 12 (checked)
I hope this helps. :-)