How do you solve 36^(x^2+9) = 216^(x^2+9)36x2+9=216x2+9?

1 Answer
May 22, 2017

x=+-sqrt((2kpii)/ln 6-9)x=±2kπiln69

for any integer kk

Explanation:

Given:

36^(x^2+9) = 216^(x^2+9)36x2+9=216x2+9

Divide both sides by 36^(x^2+9)36x2+9 to get:

1 = 6^(x^2+9) = e^((x^2+9)ln 6)1=6x2+9=e(x2+9)ln6

From Euler's identity we can deduce:

(x^2+9)ln 6 = 2kpii(x2+9)ln6=2kπi

for any integer kk

So:

x^2+9 = (2kpii)/ln 6x2+9=2kπiln6

Hence:

x = +-sqrt((2kpii)/ln 6-9)x=±2kπiln69

If k=0k=0 that gives us:

x = +-sqrt(-9) = +-3ix=±9=±3i

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Footnote

If you would like the other roots in a+bia+bi form, then you can use the formula derived in https://socratic.org/s/aEUsUcjD , namely that the square roots of a+bia+bi are:

+-((sqrt((sqrt(a^2+b^2)+a)/2)) + (b/abs(b) sqrt((sqrt(a^2+b^2)-a)/2))i)±a2+b2+a2+b|b|a2+b2a2i