/sqt/ Stupid Questions Thread

user, subtract 20 and factor using a +4 and -5

Say i have a heat distribution within a sphere modelled as u(r,t). Does "the temperature distribution in the centre is continuous" simply mean that u(0,t)_r = 0?
(_r means differentiate with respect to r)

I understand how to solve exponents when you multiply/divide bases but how the hell do you solve it when they are added or subtracted without using logs? Thank you in advance

>I understand how to solve exponents when you multiply/divide bases but how the hell do you solve it when they are added or subtracted without using logs?
Why wouldn't you use logs?

Logs aren't taught till the next grade so I'm assuming there's a way to solve this without it.

T. brainlet trying to relearn math 10 years after high school

>Logs aren't taught till the next grade so I'm assuming there's a way to solve this without it.
There isn't.

This was on an old grade 10 test. I guess the teacher is retarded then?

>There isn't.
Proof?

You can solve by intuitive analysis.
Play with it a little.

In the quadratic 12 - x - 6x^2, the terms are going to be factors of 12 (1, 2, 3, 4, 6, 12) on the left and 6 (1, 2, 3, 6) on the right. We can disregard the even factor options of 12 (2, 6) on the left because the x coefficient (-1) is odd. After this, I have to mentally shuffle round the right factors and order or signs till I find the right factors.

Question: after common-sense considerations like the above, how can I find the solutions apart from basically trial and error?