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Bài 1:
a) \(24 - (-15) - 2\)
\(=39-2\)
\(=37\)
b) \((-85) + 10 - (-85) - 50\)
\(=[(-85)-(-85)]+10-50\)
\(=0+10-50\)
\(=10-50\)
\(=-40\)
c) \(71 - (-30) - (+18) + (-30)\)
\(=[(-30)-(-30)]+71-(+18)\)
\(=0+71-18\)
\(=71-18\)
\(=53\)
d) \(-(30) - (+37) + (+37) + (-85)\)
\(=[-(+37)+(+37)]-(30)+(-85)\)
\(=0-(30)+(-85)\)
\(=(-30)+(-85)\)
\(=-115\)
e) \((35-815) - (795-65)\)
\(=(-780)-730\)
\(=-1510\)
g) \((2002-79+15) + (-79+15)\)
\(=1938+(-64)\)
\(=1874\)
Bài 2:
a) \(25 - (30+x) = x - (27-8)\)
\(25-30-x=x-27+8\)
\(x+x=25-30+27-8\)
\(2x=14\)
\(x=14\div2\)
\(x=7\)
b) \((x-12) - 15 = (20-17) - (18+x) \)
\(x-12-15=13-18-x\)
\(x-27=-5-x\)
\(x+x=-5+27\)
\(2x=22\)
\(x=22\div2\)
\(x=11\)
c) \(15 - x = 7 - (-2)\)
\(15-x=9\)
\(x=15-9\)
\(x=6\)
d) \(x - 35 = (-12) - 3\)
\(x-35=-15\)
\(x=-15+35\)
\(x=20\)
e) \(\left|5-x\right|-26=-15\)
\(\left|5-x\right|=-15+26\)
\(\left|5-x\right|=11\)
Từ đây ta có:
*Nếu \(5-x=11\)
\(x=5-11\)
\(x=-6\)
*Nếu \(5-x=-11\)
\(x=5-(-11)\)
\(x=16\)
Vậy \(x=-6;x=16\)
Bài 1
a) -(515-80+91)-(2003+80-91)= -515+80-91-2003-80+91=(80-80)+(-91+91)+(-515-2003)=0+0+(-2518)= -2518
b)-(-85)-(-71)+15+(-85)=85+71+15+-85=(85-85)+(71+15)=0+86=86
c)-(537-812)+(-163-712)-(-364)= -537+812+-163-712+364=(812-712)+(-537-136)+364=0+(-700)+364= -236
Bài 2
a)25-(x+4)= -19+3 c) I2x-5l=13
25-(x+4)= -16 suy ra 2x-5 thuộc {13;-13}
(x+4)= 25-(-16) TH1: 2x-5=13 vậy x=9
x+4 =41 TH2: 2x-5= -13 vậy x= -4
x =41-4
x =37
Tìm x biết:
a,x-5/7=1/9
b,2x/5=6/2x+1
c,11/8+13/6=85/x
d,2x-2/11=1.1/5
e,x/15=3/5+-2/3
f,x/182=-6/14.35/91
a, \(x\) - \(\dfrac{5}{7}\) = \(\dfrac{1}{9}\)
\(x\) = \(\dfrac{1}{9}\) + \(\dfrac{5}{7}\)
\(x\) = \(\dfrac{52}{63}\)
b, \(\dfrac{2x}{5}\) = \(\dfrac{6}{2x+1}\)
2\(x\).(2\(x\) + 1) = 30
4\(x^2\)+ 2\(x\) - 30 = 0
4\(x^2\) + 12\(x\) - 10\(x\) - 30 = 0
(4\(x^2\) + 12\(x\)) - (10\(x\) + 30) =0
4\(x\).(\(x\) + 3) - 10.(\(x\) +3) = 0
2 (\(x\) + 3).(2\(x\) - 5) = 0
\(\left[{}\begin{matrix}x+3=0\\2x-5=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=-3\\x=\dfrac{5}{2}\end{matrix}\right.\)
Vậy \(x\) \(\in\) {-3; \(\dfrac{5}{2}\)}
a) 460 + 85.4 = ( x + 200 ) : 4
=> x = 3000
b) => x = 2595
c) => x = 50
d) => x = 40
a)460 +85 . 4 = (x+200) :4 b)x:15+42=15+25.8
suy ra : 460+340=(x+200):4 suy ra: x:15+42=15+200
suy ra: 800= (x+200):4 suy ra : x:15+42=215
suy ra : 800.4=x+200 suy ra: x:15=215-42
suy ra : 3200=x+200 suy ra : x:15=173
suy ra: x= 3200-200 suy ra : x=173.15
suy ra : x=3000 vậy x =3000 suy ra: x=2595 vậy x = 2595
c) x-32:16=48 d)x-6:2-(48-24.2:6-3)=0
suy ra :x-2=48 suy ra : x-6:2-(48-48:6-3)=0
suy ra :x=48+2 suy ra : x-6:2-(48-8-3)=0
suy ra : x=50 suy ra : x-6:2-(40-3)=0
vậy x=50 suy ra : x-6:2 - 37=0
suy ra : x-3-37=0
suy ra : x-3=0+37
suy ra : x-3=37
suy ra : x=37+3
suy ra :x=40 vậy x= 40
Cho mình câu chả lời sớm nhất vào 4h30 chiều ngày 28/9/2021