7/(x+3)(x+10)+11/(x+10)(x+21)+13/(x+2)(x+34)= x/(x+2)(x+34)( chắc bạn sai cái cuối)
= 1/( x+ 3) - 1/( x+10) + 1/(x+ 10) - 1/( x+ 21) = x/(x+2)(x+34) - 13/ ( x+ 2). ( x+ 34)
⇔ 1/( x+ 3)- 1/(x+ 21) = x- 13/( x+ 2). ( x+ 34)
Thấy hơi sai đề chút
⇔ x+ 21- x- 3/ (x+3). ( x+ 21)= x- 13/( x+ 2). ( x+ 34)
⇔ 18/ ( x+ 3). ( x+ 21)= x- 13/( x+ 2). ( x+ 34)
Sai đề rồi bạn ơi
x/2008-1/10-1/15-1/21-....-1/120= 5/8
⇔ x/2008 - ( 1/10+ 1/15+....+ 1/120)= 5/8
Đặt B= 1/10+ 1/15+ 1/120
B: 2= 1/20+ 1/30+...+ 1/240
B: 2= 1/4.5+ 1/5.6+...+ 1/15. 16
B: 2= 1/4- 1/5+ 1/5- 1/6+...+ 1/15- 1/16
B: 2= 1/4- 1/16
B: 2= 3/16
B= 3/16 . 2
B= 3/8
⇒ x/2008- 3/8= 5/8
⇒ x/ 2008= 5/8+ 3/8
x/2008= 1
⇒ x= 2008
Vậy x= 2008
Chúc bạn học tốt!
