<s>[INST] Factore $(x+1)(x+2)(x+3)(x+4)-35$ I need to factor
$$(x+1)(x+2)(x+3)(x+4)-35$$
I know that the answer will be 
$$(x^2+5x+11)(x^2+5x-1)$$
I go out only
$$(x^2+5x)(x^2+5x+10)-11$$
Help me.
 [/INST] Put $t=x^2+5x$
Then the given expression will be $t(t+10)-11$
$\Rightarrow t^2+10t-11=t^2-t+11t-11=(t+1)(t-11)$
Now put the value of $t$
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