2 câu trả lời
Đáp án + Giải thích các bước giải:
x+11998+x+21997=x+31996+x+41995
⇔x+11998+1+x+21997+1
⇔(x+1)/1998 1998/1998+ (x+2)/1997 +1997/1997= (x+3)/1996 +1996/1996+ (x+4)/1995 +1995/1995
⇔ (x+1+1998)/1998 + (x+2+1997)/1997 = (x+3+1996)/1996 + (x+4+1995)/1995
⇔ (x+1999)/1998 + (x+1999)/1997 = (x+1999)/1996 + (x+1999)/1995
⇔ (x+1999)/1998 + (x+1999)/1997 - (x+1999)/1996 - (x+1999)/1995=0
⇔ (x+1999).(1/1998+1/1997-1/1996-1/1995)=0
⇔ x+1999=0 vì 1/1998+1/1997-1/1996-1/1995\ne0
⇔ x=-1999
Vậy phương trình có nghiệm x=-1999
\frac{x+1}{1998} +1+\frac{x+2}{1997} +1=\frac{x+3}{1996} +1+\frac{x+4}{1995} +1
⇔\frac{x+1+1998}{1998} +\frac{x+2+1997}{1997} =\frac{x+3+1996}{1996} +\frac{x+4+1995}{1995}
⇔\frac{x+1999}{1998} +\frac{x+1999}{1997}= \frac{x+1999}{1996} +\frac{x+1999}{1995}
⇔\frac{x+1999}{1998} +\frac{x+1999}{1997}- \frac{x+1999}{1996} -\frac{x+1999}{1995}=0
⇔(x+1999)(\frac{1}{1998} +\frac{1}{1997} -\frac{1}{1996} -\frac{1}{1995} )=0
Vì (\frac{1}{1998} +\frac{1}{1997} -\frac{1}{1996} -\frac{1}{1995} )khác0
=>x+1999=0
=>x=-1999