trừ hai vế của PT cho 4 . ta được

\(\dfrac{x-291}{1700}-1+\dfrac{x-293}{1698}-1+\dfrac{x-295}{1696}-1+\dfrac{x-297}{1694}-1=4-4\)

<=> \(\dfrac{x-291-1700}{1700}+\dfrac{x-293-1698}{1698}+\dfrac{x-295-1696}{1696}+\dfrac{x-297-1694}{1694}=0\)

<=> \(\dfrac{x-1991}{1700}+\dfrac{x-1991}{1698}+\dfrac{x-1991}{1696}+\dfrac{x-1991}{1694}=0\)

<=> (x-1991)\(\left(\dfrac{1}{1700}+\dfrac{1}{1698}+\dfrac{1}{1696}+\dfrac{1}{1694}\right)=0\)

<=> x - 1991 = 0 ( vì \(\dfrac{1}{1700}+\dfrac{1}{1698}+\dfrac{1}{1696}+\dfrac{1}{1694}\)luôn lớn hơn 0 với mọi x)

<=> x = 1991

vậy x=1991

https://giaibaitapvenha.blogspot.com/2017/12/toan-lop-8-ai-so-giai-phuong-trinh.html

Nếu lời giải giúp ích được cho bạn, truy cập

https://giaibaitapvenha.blogspot.com/2017/12/en-voi-do-homework-for-you-e-trai.html

Đáp án:

Có nhiều hình tam giác nha.

(n_n)

1. a) 201+20-112= 221-112= 109

    b) 2190+1029-9299= 3219-9299= -5880

    c) 999-999+999-999= 0+0=0

    d) 291-912+12910= -693+ 12910= 12217

2. a) 29x+3029= 3870

     => 29x= 3870-3029=841

     => x= 841: 29

     => x=29

    b) (x+3928)-2019= 2000000

     => x+3928= 2000000+ 2019= 2002019

     => x= 2002019

     c) -3x-201=-441

     => -3x= -441+ 201= -240

     => x= 80

     d) 291-293+x= 293

     => -2+x= 293

     =>x= 293+2=295

     e) 283+ 10^x= 1283

     => 10^x= 1283-283= 1000

     => x=3

x:5+174=1694

x:5=1694-174

x:5=1520

   x=1520.5

   x=7600

x : 5 = 1694 - 174 = 1520

x = 1520 . 5

x = 7600

1698 - x = 458

          x = 1698 - 458

          x = 1240

1698-x=458

x=1698-458

x=1240

goi so tn can tim la x (x N)

vi so tn do khi chia cho 3du 2 nen x:3du2 suy ra 2x:3du1 suy ra (2x-1)chia het cho3