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1,S=2-4-6+8+10-12-14+16+.......+1994-1996-1998+2000
S =(2-4-6+8)+(10-12-14+16)+......+(1994-1996-1998+2000)
S= 0 +0+........+0
S=0
2/ Vì 13 chia hết cho x-2
-> x-2 thuộc Ư(13)={1;13;-1;-13}
ta có bảng
x-2 | 1 | 13 | -1 | -13 |
x | 3 | 15 | 1 | -11 |
3/ Vì -15chia hết cho n-3->n-3 thuộc Ư(-15)={1;3;5;15;-1;-3;-5;-15}
Ta có bảng
n-3 | 1 | 3 | 5 | 15 | -1 | -3 | -5 | -15 |
n | 4 | 6 | 8 | 18 | 2 | 0 | -2 | -12 |
4/ n-2 thuộc Ư(3)={1;3;-1;-3}
ta có bảng
n-2 | 1 | 3 | -1 | -3 |
n | 3 | 5 | 1 | -1 |
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(X -10/1994 -1) + (X-8/1996 - 1) + (X-6/1998 - 1)+ (X-4/2000 - 1) + (X-2/2002 - 1) = (X-2002/2 - 1) + (X-2000/4 - 1) + (X-1998/6 - 1) + (X-1996/8 - 1) + (X-1994/10 - 1)
=> x-2004/1994 + x-2004/1996 + x-2004/1998 + x-2004/2000 + x-2004/2002 = x-2004/2 + x-2004/4 + x-2004/6 + x-2004/8 + x-2004/1994
=> x-2004/1994 + x-2004/1996 + x-2004/1998 + x-2004/2000 + x-2004/2002 - x-2004/2 - x-2004/4 - x-2004/6 - x-2004/8 - x-2004/1994 = 0
=> (x - 2004)(1/994 + 1/1996 + 1/1998 + 1/2000 + 1/2002 + 1/2 + 1/4 + 1/6 + 1/8) = 0
Mà (1/994 + 1/1996 + 1/1998 + 1/2000 + 1/2002 + 1/2 + 1/4 + 1/6 + 1/8) \(\ne\)0
=> x - 2004 = 0
=> x = 2004
Vậy x = 2004
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a/ (X+1)/35+1+(x+3)/33+1 =(x+5)/31+(x+7)/29+1+1
=>(x+36)/35+(x+36)/33-(x+36)/31-(x+36)/27=0
=>(X+36)(1/35+1/33-1/31-1/29)=0
=> x+36=0(vì c=vế 2 luôn luôn khác 0)
=>x=-36
b/ CMTT câu a
trừ tung phân số cho 1 ta được x=2004
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Bài 1:
$10+3(x-6)=5^{10}:5^8=5^2=25$
$3(x-6)=25-10=15$
$x-6=15:3=5$
$x=5+6=11$
Bài 2:
a. $100-[150-8(7-4)^2]=100-(150-8.3^2)=100-150+8.3^2$
$=-50+72=72-50=22$
b. $=-999-23+999-10-67=(-999+999)-10-(67+23)$
$=0-10-90=-(10+90)=-100$