Ko hiểu đề bài!

đầu tiên ta tìm số hạng của dãy :

       ( 110 - 1 ) : 1 + 1 = 110 ( số )

tiếp ta tìm tổng :

       ( 110 + 1 ) x 110 : 2 = 6105 

 ĐS : 6105

=============> CHÚC HỌC GIỎI <==============

x=-416

là đúng

đúng k nhé
 

x=-416

\(\left(2x-6\right)\left(x^2+2\right)=\left(2x-6\right)\left(8x-10\right)\)

\(\Leftrightarrow\left(2x-6\right)\left(x^2+2\right)-\left(2x-6\right)\left(8x-10\right)=0\)

\(\Leftrightarrow\left(2x-6\right)\left(x^2+2-8x+10\right)=0\)

\(\Leftrightarrow2\left(x-3\right)\left(x^2-6x-2x-12\right)=0\)

\(\Leftrightarrow2\left(x-3\right)\left(x-6\right)\left(x-2\right)=0\)

\(\Rightarrow x\in\left\{3;6;2\right\}\)

\(\left(5x-1\right)^2=\left(3x+5\right)^2\)

\(\Leftrightarrow\left(5x-1\right)^2-\left(3x+5\right)^2=0\)

\(\Leftrightarrow\left(5x-1-3x-5\right)\left(5x-1+3x+5\right)=0\)

\(\Leftrightarrow\left(2x-6\right)\left(8x+4\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-6=0\\8x+4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=3\\x=\frac{-1}{2}\end{cases}}}\)

\(\frac{109-x}{91}+\frac{107-x}{93}+\frac{105-x}{95}+\frac{103-x}{97}=-4\)

\(\Leftrightarrow\frac{109-x}{91}+1+\frac{107-x}{93}+1+\frac{105-x}{95}+1+\frac{103-x}{97}+1=0\)

\(\Leftrightarrow\frac{200-x}{91}+\frac{200-x}{93}+\frac{200-x}{95}+\frac{200-x}{97}=0\)

\(\Leftrightarrow\left(200-x\right)\left(\frac{1}{91}+\frac{1}{93}+\frac{1}{95}+\frac{1}{97}\right)=0\)

Vì \(\frac{1}{91}+\frac{1}{93}+\frac{1}{95}+\frac{1}{97}\ne0\)

\(\Rightarrow200-x=0\)

\(\Leftrightarrow x=200\)

Vậy....

làm như thế này đứng chưa:

315-x/101+313-x/103+311-x/105+309-x/107=-4

<=>(315-x/101+1)+(313-x/103+1)+(311-x/105+1)+(309-x/107+1)=-4+4

<=>x+416/101+x+416/103+x+416/105+x+416/107=0

<=>(x+416)(1/101+1/103+1/105+1/107)=0

<=>x+416=0

=>x=-416

tại s cái bước 2 lại là x + 416/101 chứ k pải là -x+416/101

(109-x)/91+(107-x)/93+(105-x)/95+(103-x)/97=-4

[(109-x)/91 +1]+[(107-x)/93 +1]+[(105-x)/95 +1]+[(103-x)/97 +1]-4=-4

(109+91-x)/91+(107+93-x)/93+(105+95-x)/95+(103+97-x)/97=-4+4

(200-x)/91+(200-x)/93+(200-x)/95+(200-x)/97=0

(200-x)(1/91+1/93+1/95+1/97)=0

Ma : 1/91+1/93+1/95+1/97\(\ne\)0

=>200-x=0

=>x=200

1,a,\(\left|x+2\right|=x+3\Leftrightarrow\orbr{\begin{cases}x+2=x+3\\x+2=-x-3\end{cases}}\)

                                      \(\Leftrightarrow\orbr{\begin{cases}x-x=3-2\\x+x=-3-2\end{cases}\Leftrightarrow\orbr{\begin{cases}0=1\left(voly\right)\\x=\frac{-5}{2}\end{cases}}}\)

b, \(|x-2|=2-x\Leftrightarrow\orbr{\begin{cases}x-2=2-x\\x-2=x-2\end{cases}}\)

                                    \(\Leftrightarrow\orbr{\begin{cases}x+x=2+2\\x-x=-2+2\end{cases}\Rightarrow x=2}\)

c,\(\left|2x-1\right|=3\Leftrightarrow\orbr{\begin{cases}2x-1=3\\2x-1=-3\end{cases}}\)

                             \(\Leftrightarrow\orbr{\begin{cases}2x=4\\2x=-2\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=-1\end{cases}}}\)

d,\(\left|x-12\right|=x\Leftrightarrow\orbr{\begin{cases}x-12=x\\x-12=-x\end{cases}\Leftrightarrow\orbr{\begin{cases}0=12\left(voly\right)\\x=6\end{cases}}}\)