All About That Base (Exponential Equations)


Solving exponential equations with different bases can be a little trickier than solving exponential equations with the same base.  Let’s have a look at this equation:


Not only are the bases, 3 and 2, not the same, we can’t even rewrite them to be the same base, like we could of this was our equation:


So what’s a poor Brightstormer to do? Well I’ll tell ya. First, we have to get every base with an x in the exponent on one side of the equation, and everything else on the other side. We split apart the crazy stuff in the exponent of 2 using the rule


Like this:


Now we can multiply both sides by 2, and get this equation:


Then divide both sides by 3x:


Whew.  That was a alot.  But we’re in really good shape now.  Remember this rule of exponents?


Let’s apply it to the left hand side of our equation.  We get


Suh-weet! Now we can take the natural log of both sides of the equation (or you can use log base 10 AKA the standard logarithm… it’s your choice!)


Use the power rule for logarithms to pull the x out front…


Divide both sides by ln(2/3) to get x all by itself…


And we’re done! Ta-da!  You can put the left hand side of the above equation into your calculator if you need to get an actual number for some reason.  If you’re still having trouble with solving exponential equations with different bases, check out these Brightstorm videos

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