Bài 1:
a) −x + 8 = −17
−x = −17 − 8
−x = −25
⇒ x = 25
Vậy x = 25
b) 35 − x = 37
x = 35 − 37
x = −2
Vậy x = −2
c) x − 45 = −17
x = −17 + 45
x = 28
Vậy x = 28
d) |x + 1| = 20 (>0)
TH1: x + 1 = 20 TH2: x + 1 = −20
x = 20 − 1 x = −20 − 1
x = 19 x = −21
Vậy x∈\(\left\{-21;19\right\}\)
e) |x − 3| − 16 = −4
|x − 3| = −4 + 16
|x − 3| = 12 (>0)
TH1: x − 3 = 12 TH2: x − 3 = −12
x = 12+3 x = −12 + 3
x = 15 x = −9
Vậy x∈\(\left\{-9;15\right\}\)
b) 35 − x = 37
x = 35 − 37
x = −2
Vậy x = −2
Bài 2:
a) (144 − 97) − 144
= 144 − 97 − 144
= (144 − 144) − 97
= − 97
b) (−145) − (18 − 145)
= −145 − 18 + 145
= (−145 + 145) − 18
= −18
c) (27 + 514) − (486 − 73)
= 27 + 514 − 486 + 73
= (27 + 73) + (514 − 486)
= 100 + 28
= 128
d) (38 − 29 + 43) − (43 + 38)
= 38 − 29 + 43 − 43 − 38
= (−38 + 38) + (−43 + 43) − 29
= 0 + 0 − 29
= −29
Bài 2:
a) \(\left(144-97\right)-144=144-97-144=-97\)
b) \(\left(-145\right)-\left(18-145\right)=-145-18+145=-18\)
c) \(\left(27+514\right)-\left(486-73\right)=27+514-486+73=100-28=72\)
d) \(\left(38-29+43\right)-\left(43+38\right)=38-29+43-43-38=-29\)
Bài 1:
a) Ta có: -x+8=-17
nên -x=-25
hay x=25
b) Ta có: \(35-x=37\)
nên x=35-37
hay x=-2
c) Ta có: \(x-45=-17\)
nên x=-17+45
hay x=28
d) Ta có: \(\left|x+1\right|=20\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=20\\x+1=-20\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=19\\x=-21\end{matrix}\right.\)
e) Ta có: \(\left|x-3\right|-16=-4\)
\(\Leftrightarrow\left|x-3\right|=12\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=12\\x-3=-12\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=15\\x=-9\end{matrix}\right.\)
