<p>2^2x = 8^(x-1)</p>
<p>how do you do it? I mean besides plugging in all the answers.. (which is what I do. it works, but it isn't as efficient)</p>
<p>8 = 2^3
Therefore,
8^(x-1) = 2^3(x-1)
2^(2x) = 2^3(x-1)
2x = 3(x-1)
2x = 3x - 3
x = 3</p>
<p>It’s just playing with exponents. This is important not only in SAT Math, but in advanced math where you need the basics to construct more complex equations.</p>
<p>2^2x = 8^(x-1)</p>
<p>is the same as </p>
<p>2^2x = (2^3)^(x-1)</p>
<p>and using exponential rules you know to multiply extra power (ex. (2^3)^(x-1) is 2^(3x-3)</p>
<p>thus it becomes 2^2x = 2^(3x-3)</p>
<p>using basic algebra you now know that you can set the two exponents together, since the base is the same.</p>
<p>2x= 3x-3 </p>
<p>x = 3</p>
<p>thanks. love this site.</p>
<p>or u can use the properties of logarithms and move the exponents that way. Have you had algebra II??</p>
<p>yea I’m in precalc. I’d rather avoid logs, and use simple exponent rules.</p>
<p>Yup, as long as the bases are equal, you can set up the exponents as a equation.</p>
<p>Paradoxically, it’s actually a logarithmic rule.</p>
<p>Well, Logarithms are intertwined with exponents.</p>