x x 400 = 1600
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\(\frac{4}{5}x\frac{1}{20\%}+0,08=4,08\)
\(2001:25-1999:25=0,08\)
\(75x1,25=93,75\)
\(56x2,5x400=56000\)
\(1600:1,25=1280\)
\(k\)\(nha♥♥♥♥\)
x chia hết cho 39, 65, 91
=> x \(\in\) BC ( 39, 65, 91 ) và 400 < x < 1600
BCNN ( 39, 65, 91 ) = 3 . 5 . 7. 13 = 1365
BC ( 39, 65, 91 ) = B ( 1365 ) = \(\left\{0,1365,....\right\}\)
Vì 400< x < 1600 => x = 1365
Vậy x = 1365
Vì \(x\) \(⋮\) \(39\), \(x\) \(⋮\) 65, \(x\) \(⋮\) \(91\) \(\left(x\in N\right)\)
\(\Rightarrow x\in BC\left(39;65;91\right)\)
Ta có:
\(39=13.3\)
\(65=13.5\)
\(91=13.7\)
\(\Rightarrow BCNN\left(39;65;91\right)=13.3.5.7=1365\)
\(\Rightarrow x\in BC\left(39;65;91\right)=\left\{0;1365;2730;...\right\}\)
Vì \(400< x< 1600\)
\(\Rightarrow x=1365\)
Vậy \(x=1365\).
\(\sqrt{1600^2-400^2}=400\sqrt{15}\)
\(\sqrt{1200^2-300^2}=2^2\cdot3\cdot5^2\sqrt{15}\)
50+100+200+400+800+1600+3200+6400+12800+25600+51200+10000000=10102350
=> \(\left[\frac{x-1}{2}+1\right]^2=1600\)
=> \(\left[\frac{x-1}{2}+1\right]^2=40^2\)
=> \(\left[\frac{x-1}{2}+1\right]=40^{ }\)
=> \(\frac{x-1}{2}=39\)
=> x - 1 = 39.2
=> x - 1 = 78
=> x=79
Từ 1→x có:(x-1):2+1
Do đó ta có:1+3+5+...+x=1600
<=>[(x+1).(x-1)/2+1]:2=1600
<=>(x+1).(x-1)/2+1=1600.2=3200
<=>(x+1).(x-1)/2+2/2=3200
<=>(x+1).(x-1+2)/2=3200
<=>(x+1).(x+1)/2=3200
<=>(x+1)^2=3200.2=6400
<=>x+1=80=-80
<=>x=79 hoặc x=-81
( x + 10 ) : 8 = 1600
( x + 10 ) = 1600 . 8
( x + 10 ) = 12800
x = 12800 - 10
x = 12790
( x + 10 ) : 8 = 1600
x + 10 = 1600 x 8 = 12800
x = 12800 - 10
x = 12790
x = 4 nha bạn
x x 400 = 1600
x = 1600 :400
x = 4 ai tk mk mk tk lai