I know this probably is a silly stupid question, but I just don't get it. I'm currently doing Khan Academy pre-algebra and stumbled upon an awkward problem. I assume that:
$-5-8^{2}=59$
Because -8 squared is 64 and et cetera. But the right answer is actually -69. I sincerely don't get why. I told my wife, she's sure it should be 59 too. Can someone explain to me how comes it is -69?
On
It's just convention in the priority of the operations. Exponents are done before any addition/substraction If we add brackets, your expression becomes:
$$ ( -5 )- ( 8^2 ) $$
Thus it is $-69$.
Why was that chose? Simple, as you said in you answer, there is no difference between $(-8)^2$ and $8^2$ so $(-5) + ((-8)^2)$ could just have been written $(-5) + (8^2)$. Not as interesting as the other priority order.
The correct order of the operations is: first calculate the powers than add the results. So in you case: $$-5-8^2=-5-(8^2)=-5-64=-69$$