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a) 7^2.5-(2x+1)=630:9
b) (10-4x)+120:2^3=17
c) [124-(20-4X)]:30+7=11
d) |2x-5|=1
nhớ ghi đầy đủ bước nhá
\(a\)\(.\)\(7^2.5-\left(2x+1\right)=630:9\)
\(49.5-\left(2x+1\right)=70\)
\(245-\left(2x+1\right)=70\)
\(2x+1=245-70\)
\(2x+1=175\)
\(2x=175-1\)
\(2x=174\)
\(x=174:2\)
\(x=87\)
Vậy \(x=87\)
\(b.\)\(\left(10-4x\right)+120:2^3=17\)
\(\left(10-4x\right)+120:8=17\)
\(\left(10-4x\right)+15=17\)
\(10-4x=17-15\)
\(10-4x=2\)
\(4x=10-2\)
\(4x=8\)
\(x=8:4\)
\(x=2\)
Vậy \(x=2\)
\(c.\)\(\left[124-\left(20-4x\right)\right]:30+7=11\)
\(\left[124-\left(20-4x\right)\right]:30=11-7\)
\(\left[124-\left(20-4x\right)\right]:30=4\)
\(\left[124-\left(20-4x\right)\right]=4.30\)
\(\left[124-\left(20-4x\right)\right]=120\)
\(124-20+4x=120\)
\(104+4x=120\)
\(4x=120-104\)
\(4x=16\)
\(x=16:4\)
\(x=4\)
Vậy \(x=4\)
\(d.\)\(\left|2x+5\right|=1\)
\(\Rightarrow2x+5\in\left\{-1;1\right\}\)
\(\Rightarrow2x\in\left\{-6;-4\right\}\)
\(\Rightarrow x\in\left\{-3;-2\right\}\)
Vậy \(x\in\left\{-3;-2\right\}\)
học tốt
a) \(7^2\cdot5-\left(2x+1\right)=630:9\)
\(\Leftrightarrow49\cdot5-2x-1=70\)
\(\Leftrightarrow244-2x=70\)
\(\Leftrightarrow2x=244-70\)
\(\Leftrightarrow2x=174\)
\(\Leftrightarrow x=87\)
Vậy x=87.
b) \(\left(10-4x\right)+120:2^3=17\)
\(\Leftrightarrow10-4x+120:8=17\)
\(\Leftrightarrow10-4x+15=17\)
\(\Leftrightarrow25-4x=17\)
\(\Leftrightarrow4x=25-17=8\)
\(\Leftrightarrow x=2\)
Vậy x=2
c)\([124-\left(20-4x\right)]:30+7=11\)
\(\Leftrightarrow\left(124-20+4x\right):30=4\)
\(\Leftrightarrow104+4x=120\)
\(\Leftrightarrow4x=120-104=16\)
\(\Leftrightarrow x=4\)
Vậy x=4
d) \(|2x-5|=1\)
\(\Leftrightarrow\orbr{\begin{cases}2x-5=1\\2x-5=-1\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}2x=6\\2x=4\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=2\end{cases}}\)
Vậy \(x\in\text{ }\left\{3;2\right\}\)
a) 72.5–(2x+1)=630:972.5–(2x+1)=630:9
⇒245–2x–1=70⇒245–2x–1=70
⇒−2x=−22+70⇒−2x=−22+70
⇒−2x=−174⇒−2x=−174
⇒x=87⇒x=87
b)(10−4x)+120:23=17
10−4x+15=17
10−4x=17−15
10−4x=2
4x=10−2
4x=8
x=8:4
x=2
72 x 5-(2x+1)=630:9
<=> 49 x 5-2x-1=70
<=> 245-2x-1=70
<=> -2x+244=70
<=> -2x=-174
<=> x=87
tìm x biết:
a, 72.5-(2x+1)=630:9
49.5-(2x+1)=70
245-(2x+1)=70
2x+1=245-70
2x+1=175
2x=175-1
2x=174
x=174:2
x=87
Vậy x=87
b, (10-4x)+120:23=17
(10-4x)+120:8=17
(10-4x)+15=17
10-4x=17-15
10-4x=2
4x=10-2
4x=8
x=8:4
x=2
Vậy x=2
Bài 1:
a. $(-20)+x=-30$
$x-20=-30$
$x=-30+20=-(30-20)=-10$
b.
$(-10)-x=-20$
$x=(-10)-(-20)=-10+20=20-10=10$
c. Đề sai. Bạn xem lại.
d.
$x+(-3)=-7$
$x=-7-(-3)=-7+3=-(7-3)=-4$
e.
$x-(-5)=-9$
$x=(-9)+(-5)=-14$
f.
$x(-11)=12$
$x=\frac{12}{-11}=\frac{-12}{11}$
h.
$2x-10=20$
$2x=20+10=30$
$x=30:2=15$
l.
$4x-8=-8$
$4x=-8+8=0$
$x=0:4=0$
k.
$-12-(-2)x=-8$
$(-2)x=-12-(-8)=-12+8=-(12-8)=-4$
$x=(-4):(-2)=2$
Bài 2:
a. $-20-(10-x)=-3$
$10-x=-20-(-3)=-20+3=-(20-3)=-17$
$x=10-(-17)=10+17=27$
b.
$14+(14-x)=-2$
$14-x=-2-14=-16$
$x=14-(-16)=14+16=30$
c.
$-15-(x-3)=-7$
$x-3=-15-(-7)=-15+7=-8$
x=-8+3=-5$
d.
$(x+4)+(-20)=-8$
$x+4=-8-(-20)=-8+20=12$
$x=12-4=8$
e.
$-2x-2=-4$
$-2x=-4+2=-2$
$x=(-2):(-2)=1$
f.
$-2x+4=-4$
$-2x=-4-4=-8$
$x=(-8):(-2)=4$
l.
$-12-(-2)x=-2-4=-6$
$(-2)x=-12-(-6)=-12+6=-6$
$x=(-6):(-2)=3$
a,17-3x-11=31-2x
=> 6 - 3x = 31 - 2x
=> 6 - 31 = - 2x + 3x
=> x = - 25
Vậy x = - 25
b,12 - | x + 3 |=5
=> | x + 3 | = 7
\(\Rightarrow\orbr{\begin{cases}x+3=7\\x+3=-7\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=4\\x=-10\end{cases}}\)
Vậy \(x\in\left\{4;-10\right\}\)
c,4 x+ (-46) = -30
=> 4x = - 30 + 46
=> 4x = 16
=> x = 4
Vậy x = 4
d, -20 + (5x - 5 ) = 60
= > - 20 + 5x - 5 = 60
=> 5x = 60 + 20 + 5
=> 5x = 85
=> x = 17
Vậy x = 17
e, 10 + |1 - 2x |= 15
=> | 1 - 2x | = 5
\(\Rightarrow\orbr{\begin{cases}1-2x=5\\1-2x=-5\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x=-4\\2x=6\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=-2\\x=3\end{cases}}\)
Vậy \(x\in\left\{-2;3\right\}\)
Dài qua lần sau đừng đăng nhiều như v
Tự nghĩ k đc à
@@ Học tốt @@
## Chiyuki Fujito
a. 4(2x+7)-3(3x-2)=24
=> 8x+28-9x+6=24
=> -x+34=24
=> -x=-10=> x=10
b. 2(x-1)+3(x-2)=x-4
=> 2x-2+3x-6=x-4
=> 5x-8=x-4
=> 5x-x=-4+8
=> 4x=4=> x=1
c. [124-(20-4x)]:30+7=11
=> (124-20+4x):30=4
=> (104+4x):30=4
=> 104+4x=120
=> 4x=96 => x=24
1.
a) [124 - (20 - 4x)] : 30 + 7 = 11
=> [124 - (20 - 4x)] : 30 = 11 - 7
=> [124 - (20 - 4x)] : 30 = 4
=> 124 - (20 - 4x) = 4 x 30
=> 124 - (20 - 4x) = 120
=> 20 - 4x = 124 - 120
=> 20 - 4x = 4
=> 4x = 20 - 4
=> 4x = 16
=> x = 16 : 4
=> x = 4
Vậy x = 4
b) |2x - 5| = 1
TH1: 2x - 5 = 1
=> 2x = 1 + 5
=> 2x = 6
=> x = 6 : 2
=> x = 3
TH2: 2x - 5 = -1
=> 2x = -1 + 5
=> 2x = 4
=> x = 4 : 2
=> x = 2
Vậy x = 3 hoặc x = 2
a) 72,5 - (2x + 1) = 630 : 9
⇒ 72,5 - (2x + 1) = 70
⇒ 2x + 1 = 2,5
⇒ 2x = 1,5
⇒ x = 0,75
b) (10 - 4x) + 120 : 23 = 17
⇒ (10 - 4x) + 120 : 8 = 17
⇒ (10 - 4x) + 15 = 17
⇒ 10 - 4x = 2
⇒ 4x = 8
⇒ x = 2
Vậy x = 2