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a) 1/2.x+3/5.(x-2)=3
<=>1/2.x+3/5.x-6/5=3
<=>11/10.x-6/5=3
<=>11/10x=41/10
<=>x=41/11
b) (3x-4).(5x+15)=0
<=>3x-4=0 hoặc 5x+15=0
<=>x=4/3 hoặc x=-3
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5(x-2)-125=15
=>\(5\left(x-2\right)=15+125=140\)
=>x-2=28
=>x=28+2=30
Câu trả lời:
5. (𝑥 − 2) − 125 = 15
5. ( x - 2) = 125 - 15
5. ( x - 2) = 110
x - 2 = 110 : 5
x - 2 = 22
x = 22 - 2
x = 20
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Câu 4:
\(A=7^{2022}-7^{2021}+7^{2020}-7^{2019}+...+7^2-7\\ \Rightarrow7A=7^{2023}-7^{2022}+7^{2021}-7^{2020}+...+7^3-7^2\\ \Rightarrow7A+A=7^{2023}-7^{2022}+...+7^3-7^2+7^{2022}-7^{2021}+...+7^2-7\\ \Rightarrow8A=7^{2023}-7\\ \Rightarrow A=\dfrac{7^{2023}-7}{8}\)
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a) Ta có: \(\widehat{xOy}+\widehat{yOz}=180^0\)(hai góc kề bù)
\(\Leftrightarrow\widehat{zOy}+140^0=180^0\)
hay \(\widehat{yOz}=40^0\)
Vậy: \(\widehat{yOz}=40^0\)
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25-(x+5)= -415 - (15 - 415)
<=> 25 - x - 5 = -415 - 15 + 415
<=> -x = -415 -15 + 415 - 25
<=> -x = -40
<=> x = 40
k ghi lại đề nha :>
\(25-x-5=415-\left(-400\right)\))
20 - x = -415 + 400
20 - x = -15
-x = -15 - 20
-x = -35
x = 35
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![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
a. $132-468-(-215)=132-468+215=(132+215)-468$
$=347-468=-121$
b.
$(144-97)-156=47-156=-109$
c.
$(-145)-(18-145)=-145-18+145=(-145+145)-18=0-18=-18$
d.
$115+(-15+27)=115-15+27=100+27=127$
e.
$(24+614)-(386-76)=638-310=328$
Câu 2:
a.
$(-105)+x=-217$
$x-105=-217$
$x=-217+105=-112$
b.
$x-67=-23$
$x=-23+67=44$
c.
$4(3-x)=28$
$3-x=28:4=7$
$x=3-7=-4$
d.
$5[x+(-81)]=400$
$x-81=400:5=80$
$x=80+81=161$
e.
$140:(x+108)=7$
$x+108=140:7=20$
$x=20-108=-88$
f.
$-27+(-x)=-104$
$-28-x=-104$
$x=-28-(-104)=-28+104=76$
-2
Câu 15: \(x=-2\)