Can’t remember why in the 4th line another minus appears in front of the 5 besides the one from division. Pls help me I’m feeling stupid

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From what I can tell, the other minus is a mistake. In fact, if you put the whole first line into a calculator, you get -2^-7 as the answer, which is what you also get if there's only 1 minus in front of the 5.
What does the double dot : represent here? If it’s division, then 1/(a^x) = a^-x by definition

But if it’s multiplication, it looks redundant and they could have just skipped from line 3 to line 5
Assuming : is division the answer at that step is wrong and should be -2^1

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