x + 5 = 98
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\(A=20\times21+21\times22+...+99\times100\)
\(3\times A=20\times21\times\left(22-19\right)+21\times22\times\left(23-20\right)+...+99\times100\times\left(101-98\right)\)
\(=20\times21\times22-19\times20\times21+...+99\times100\times101-98\times99\times100\)
\(=99\times100\times101-19\times20\times21\)
Suy ra \(A=\frac{99\times100\times101-19\times20\times21}{3}=360640\)
\(B=3\times4\times5+4\times5\times6+...+98\times99\times100\)
\(4\times B=3\times4\times5\times\left(6-2\right)+4\times5\times6\times\left(7-3\right)+...+98\times99\times100\times\left(101-97\right)\)
\(=3\times4\times5\times6-2\times3\times4\times5+...+98\times99\times100\times101-97\times98\times99\times100\)
\(=98\times99\times100\times101-2\times3\times4\times5\)
Suy ra \(B=\frac{98\times99\times100\times101-2\times3\times4\times5}{4}=24497520\)
(x+5)/100+(x+5)/99=(x+5)/98+(x+5)/97
(x+5)/100+(x+5)/99-(x+5)/98-(x+5)/97=0
(x+5)(1/100+1/99-1/98-1/97)=0
suy ra x+5=0
x=-5
1. \(x-8+32=68\)
\(x-8=68-32\)
\(x-8=36\)
\(x=36+8\)
\(x=44\)
_____
2. \(x+8+32=68\)
\(x+8=68-32\)
\(x+8=36\)
\(x=36-8\)
\(x=28\)
_____
3. \(98-x+34=43\)
\(98-x=43-34\)
\(98-x=9\)
\(x=98-9\)
\(x=89\)
_____
4. \(98+x-34=43\)
\(98+x=43+34\)
\(98+x=77\)
\(x=77-98\)
\(x=-21\)
_____
5. \(x:5:4=800\)
\(x:5=800.4\)
\(x:5=3200\)
\(x=3200.5\)
\(x=16000\)
_____
6. \(18+x=384:8\)
\(18+x=48\)
\(x=48-18\)
\(x=30\)
_____
7. \(\left(84,6-2\times x\right):3,02=5,1\)
\(84,6-2.x=5,1.3,02\)
\(84,6-2.x=15,402\)
\(2.x=84,6-15,402\)
\(2.x=69,198\)
\(x=69,198:2\)
\(x=34,599\)
_____
8. \(x\times5=120:6\)
\(x.5=20\)
\(x=20:5\)
\(x=4\)
_____
9. \(\left(15\times24-x\right):0,25=100:0,25\)
\(\left(15.24-x\right):0,25=400\)
\(15.24-x=400.0,25\)
\(15.24-x=100\)
\(360-x=100\)
\(x=360-100\)
\(x=260\)
1,x-8+32=68
=>x-8=68-32=36
=>x=36+8=42
2,x+8+32=68
=>x+8=68-32=36
=>x=36-8=28
3,98-x+34=43
=>98-x=43-34=9
=>x=98-9=89
4,98+x-34=43
=>98+x=43+34=77
=>x=77-98=-21
5,x:5:4=800
=>x:20=800
=>x=800x20=16000
6,18+x=384:8=48
=>x=48-18=30
7,(84,6-2x):3,02=5,1
=>84,6-2x=5,1x3,02=15,402
=>2x=84,6-15,402=69,198
=>x=69,198:2=34,599
8,5x=120:6=20
=>x=20:5=4
9,(15x24-x):0,25=100:0,25=400
=>360-x=400x0,25=100
=>x=360-100=260.
\(\Leftrightarrow6-3x+5x-30=-98\\ \Leftrightarrow2x=-74\\ \Leftrightarrow x=-37\)
\(3\left(2-x\right)+5\left(x-6\right)=-98\\ 6-3x+5x-30=-98\\ 2x-24=-98\\ 2x=-74\\ x=-37\)
Lời giải:
$7(x+9)-3(5-x)=98$
$\Leftrightarrow 7x+63-15+3x=98$
$\Leftrightarrow 10x+48=98$
$\Leftrightarrow 10x=50$
$\Leftrightarrow x=5$
\(7\times\left(x+9\right)-3\times\left(5-x\right)=98\)
\(7x+63-15+3x=98\)
\(10x+48=98\)
\(10x=98-48\)
\(10x=50\)
\(x=5\)
Vậy: \(x=5\)
câu 1
=> x+1/2+x+1/3+x+1/4-x-1/5-x-1/6=0
=> (x+x+x-x-x)+(1/2+1/3+1/4-1/5-1/6)=0
=> x+43/60=0
=> x = -43/60
câu dưới làm tương tự bạn nhé!
Nhân chia trước cộng trừ sau :
98 x 56 + 500 - 38 + 2 x 5 x 5 - 6000 =5488 + 500 - 38 + 50 - 6000 = 0
k mình nha
hok tốt
x+5=98
x=98-5
x=93
x + 5 = 98
=> x = 98 - 5
=> x = 93
• ✔ Mk nha