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5x^3 = 5(3)^3 = 5 (3)(3)(3) = 135

What if x = -2?  Be careful!

5x^3 = 5 (-2)^3 = 5 (-2)(-2)(-2) = -40


TRY IT:

Write out what  3x^4 means:

Let x = 2 and simplify:

Let x = -5 and simplify:


Here's something a little messier:

What does this thing mean?

100 n^2 m^6

The number hangs around in front... and we can expand out those exponents:

100nnmmmmmm

So, why do we have exponents?

Look at this thing!

x^590