let's say the number is "a", negative "a" is just -a
twice that value, is 2*-a or -2a
now 4 less than that, is -2a - 4
now, their produc it 286
[tex]\bf (-a)(-2a-4)=286\implies 2a^2+4a=286\implies 2a^2+4a-286=0
\\\\\\
\begin{array}{lcclll}
a^2&+2a&-143&=0\\
&\uparrow &\uparrow \\
&-11+13&-11\cdot 13
\end{array} \implies (a+13)(a-11)=0
\\\\\\
\begin{cases}
a+13=0\implies &a=-13\\
a-11=0\implies &a=11
\end{cases}[/tex]
so.. since we started with "a" as positive but multiplied by -1, then "11" is out fellow
both values do produce 286 btw
but 11 is positive, times -1 is -11
