Giải thích các bước giải:
Bài `1`
`f)`
`12,7 - 17,2 + 199,9 - 22,8 - 149,9`
`=-17,2-22,8+199,9-149,9+12,7`
`=(-17,2-22,8)+(199,9-149,9)+12,7`
`=-40+50+12,7`
`=10+12,7`
`=22,7`
`i)`
`[2^7 .9^2]/[3^3 .2^5]`
`=[2^7 .(3^2)^2]/[3^3 .2^5]`
`=[2^7 .3^4]/[3^3 .2^5]`
`=[2^2 .3]/[1.1]`
`=12`
Bài `2`
`|x+5|-6=9`
`=>|x+5|=9+6`
`=>|x+5|=15`
`=>`\(\left[ \begin{array}{l}x+5=15\\x+5=-15\end{array} \right.\)
`=>`\(\left[ \begin{array}{l}x=15-5\\x=-15-5\end{array} \right.\)
`=>`\(\left[ \begin{array}{l}x=10\\x=-20\end{array} \right.\)
