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a ) x + 36 =98
x = 98 -36
x = 62
x * 8 = 56
x = 56 : 8
x = 7
b ) 16 + 32 = 48
39 + 25 = 64
c) tính nhanh :
36 + 69 + 31 + 64
= ( 36 + 64 ) + ( 69 + 31 )
= 100 + 100
= 200
12 + 78 + 25 + 75
= (12 + 78 ) + ( 25 + 75 )
= 90 + 100
= 190
a) 2x-145=71
2x=71+145
2x=216
x=216:2
x=108
b) 98-x+41=75
139-x=75
x=139-75
x=64
1.
a, (x+50)*2=220
=> 2x+100=220
=> 2x = 120
=> x= 60
b, (2x-75)*12=144
=> 24x-900=144
=> 24x=1044
=> x= 43,5
c, (47-3x)=5
=> 47-3x=5
=> 3x=42
=> x= 14
A. ( x + 50 ) x 2= 220
=> 2x + 100 = 220
=> 2x = 220 - 100
=> 2x = 120
=> x = 120 : 2
=> x = 60
B. ( 2x - 75 ) x 12 = 144
=> (2x - 75) x 12 = 144
=> 2x - 75 = 144 : 12
=> 2x - 75 = 12
=> 2x = 75 + 12
=> 2x = 87
=> x = 87 : 2 = 43,5
C. 47 - 3x = 5
=> 3x = 47 - 5 = 42
=> x = 42 : 3
=> x = 14.
2)1 + 2 + 3 + 4 + 5 +..+ X = 2550
=> \(\frac{x.\left(x+1\right)}{2}\)=2550
=> x.(x+1) = 2550 x 2 = 5100. Mà không có 2 số liên tiếp nào nhân với nhau bằng 5100 nên x không thỏa mãn đề bài.
3)Đề sai nha bạn.
Theo bài ra,ta có:
720 : a
540 : a
\(\Rightarrow\)a \(\in\)Ư { 720 ; 540 }
720 = \(2^4\). 3\(^2\).5
540 = \(2^2\).\(3^2\). 5
ƯCLN ( 720;540 ) = 2\(^2\).\(3^2\).5 = 180
ƯC ( 720;540 ) = { 1;;2;3;4;5;6;9;10;18;12;15;90;;60;36;45;30;20;180}
Mà 75 < a <98
Nên a = 90
\(a,1357-\left(964+357\right)-\left(36+120\right)=1357-964-357-36-120\)
\(=1000-1000-120=-120\)
\(b,10000-\left(137+572\right)+\left(263-291\right)=10000-137-572+263-291\)
\(=10000-709-291+263=10000-1000+263=9000+263=9263\)
\(c,35\cdot125+35\cdot75-70\cdot50=35\cdot125+35\cdot75-35\cdot100\)
\(=35\cdot\left(125+75-100\right)=35\cdot100=3500\)
(\(\cdot\)là nhân nhé bạn)
\(d,2-4+6-8+...+98-100=-2-2-...-2\)
(50 số hạng -2)
\(=\left(-2\right)\cdot50=-100\)
Làm lại câu d:
\(d,2-4+6-8+...+98-1000=-2-2-...-2+98-1000\)
(49 số -2)
\(=\left(-2\right)\cdot49+98-1000=-98+98-1000=1000\)
\(\dfrac{1}{5}\left(x+\dfrac{1}{5}\right)+\dfrac{2}{5}\left(x+\dfrac{5}{3}\right)=\dfrac{98}{75}\\ =>\dfrac{1}{5}x+\dfrac{1}{25}+\dfrac{2}{5}x+\dfrac{2}{3}=\dfrac{98}{75}\\ =>\dfrac{3}{5}x=\dfrac{98}{75}-\dfrac{2}{3}-\dfrac{1}{25}=\dfrac{3}{5}\\ =>x=1\)
\(\dfrac{1}{5}\left(x+\dfrac{1}{5}\right)+\dfrac{2}{5}\left(x+\dfrac{5}{3}\right)=\dfrac{98}{75}\\ \Rightarrow\dfrac{1}{5}x+\dfrac{1}{25}+\dfrac{2}{5}x+\dfrac{2}{3}=\dfrac{98}{75}\\ \Rightarrow\left(\dfrac{1}{5}x+\dfrac{2}{5}x\right)+\left(\dfrac{1}{25}+\dfrac{2}{3}\right)=\dfrac{98}{75}\\ \Rightarrow\dfrac{3}{5}x+\dfrac{53}{75}=\dfrac{98}{75}\\ \Rightarrow\dfrac{3}{5}x=\dfrac{98}{75}-\dfrac{53}{75}\\ \Rightarrow\dfrac{3}{5}x=\dfrac{45}{75}=\dfrac{3}{5}\\ \Rightarrow x=\dfrac{3}{5}:\dfrac{3}{5}\\ \Rightarrow x=1\)
X + 75 - 98 = 75 - 98
X + 75 - 98 = -23
X + 75 = -23 + 98
X = 75 - 75
X = 0