`1, |x+4|-5=4-(-3)`
`<=> |x+4|-5=4+3`
`<=> |x+4|=7+5`
`<=> |x+4|=12`
`<=>`\(\left[ \begin{array}{l}x+4=12\\x+4=-12\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=12-4\\x=-12-4\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=8\\x=-16\end{array} \right.\)
`2, S=1+3+3^2+....+3^99`
`3S=3+3^2+3^3+.....+3^100`
`3S-S=(3+3^2+....+3^100)-(1+3+....+3^99)`
`2S=3^100-1`
`2S+1=3^100`
`=> 2S+1` là lũy thừa của `3` `(đpcm)`