How to know if equation can be solved by factorising before trying? So, I have core 1 test tomorrow and there is a lot of solving of quadratic equations without calculator and my weakest point is the time I waste in trying to factorise and equation but then it ends up it doesn't factorise or the opposite way in which I use equation while I could've done factorising. Is there any way you can know if equation factorise or not?

Two ways.  The first is particularly useful if the leading coefficient $a$ (as in $ax^2$) is $1$:  If two factors $(x-m)(x-n)$ exist with $m$ and $n$ integers (or even rational) then $m$ and $n$ wil always be factors the constanc coefficient $c$.
This means you need to try very few combinations, since depending on the sign of $c$ 
of the factors will will always be dictated by $b$.
For example, 
$$ x^2 +6x +10$$
could only have $m,n$ as $(1,10)$ or $(2,5)$; since neither of those add up to $6$ you can't factor this with easy factors.
The other way is to find $b^2-4ac$.  If that is a perfect square, then the equation can be factored nicely.  If not, then at least you are halfway toward finding the roots using the quadratic formula.
