How to Strike Through Text in LaTeX?

[karush]

Simplify. Assume that $n$ and $m$ are positive integers,
$a>b$, and $a>2$.$\frac{\left(a+1\right)!}{\left(a-2\right)!}$

was helping a friend with this but was clueless
I know that n! $=n(n-1)(n-2) ... $

 

[mathmari]

We have that $$(a+1)!=(a+1)\cdot a\cdot (a-1)\cdot (a-2)\cdots 1=(a+1)\cdot a\cdot (a-1)\cdot (a-2)!$$

 

[karush]

So finally
$$\frac{\left(a+1\right)!}{\left(a-2\right)!}=\frac{\left(a+1\right)a\left(a-1\right)\left(a-2\right)...}{\left(a-2\right)!}=\left(a+1\right)a\left(a-1\right)$$

 

[MarkFL]

So finally
$$\frac{\left(a+1\right)!}{\left(a-2\right)!}=\frac{\left(a+1\right)a\left(a-1\right)\left(a-2\right)...}{\left(a-2\right)!}=\left(a+1\right)a\left(a-1\right)$$

While that is certainly correct, I think a more clear notation would be:

$$\frac{(a+1)!}{(a-2)!}=\frac{(a+1)a(a-1)\cancel{(a-2)!}}{\cancel{(a-2)!}}=a(a+1)(a-1)$$

 

[karush]

how is a strike though done with latex didn't see a tool for that on the menu?

 

[MarkFL]

how is a strike though done with latex didn't see a tool for that on the menu?

I used the \cancel{} command in my post...you can find 2 types of strikethrough in the "algebra" section of the "Quick $\LaTeX$ tool at the bottom right. :)