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a: =12,7-40+50=12,7+10=22,7

a) |x| = 1212

=> x = 1212 hoặc -1212

T_T các câu kia tườn tự vậy thôi bạn, dài quá @_@

học tốt -_-"

a) \(\left|x\right|=1212\)

\(\Rightarrow\orbr{\begin{cases}x=1212\\x=-1212\end{cases}}\)

b) \(\left|2x+1212\right|=3434\)

\(\Rightarrow\orbr{\begin{cases}2x+1212=3434\\2x+1212=-3434\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}2x=2222\\2x=-4646\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1111\\x=-2323\end{cases}}\)

\(\frac{a}{b+c}=\frac{b}{a+c}=\frac{c}{a+b}=\frac{a+b+c}{2\left(a+b+c\right)}=\frac{1}{2}\)

\(2\left(2-x\right)\cdot2\cdot\left(2-x\right)\cdot1212\cdot\left(x-2\right)\cdot2\cdot\left(x-2\right)\cdot2=0\)

\(4\left(2-x\right)^2\cdot4848\left(x-2\right)^2=0\)

\(19392\left(2-x\right)^2\left(x-2\right)^2=0\)

\(\left(2-x\right)^2\left(x-2\right)^2=0\)

\(TH1:\left(2-x\right)^2=0\Rightarrow2-x=0\Rightarrow x=2\)

\(TH2:\left(x-2\right)^2=0\Rightarrow x-2=0\Rightarrow x=2\)

Vậy x = 2

<br class="Apple-interchange-newline"><div id="inner-editor"></div>2(2−x)·2·(2−x)·1212·(x−2)·2·(x−2)·2=0

4(2−x)2·4848(x−2)2=0

19392(2−x)2(x−2)2=0

(2−x)2(x−2)2=0

TH1:(2−x)2=0⇒2−x=0⇒x=2

TH2:(x−2)2=0⇒x−2=0⇒x=2

 x = 2

a+b+c = 0 => a+b=-c ; b+c=-a ; c+a=-b

=> (1+a/b).(1+b/c).(1+c/a) = a+b/b . b+c/c . c+a/a = -c/b . (-a)/c . (-b)/a = -abc/abc = -1

k mk nha

Ta có:                                  \(A=\left(-7\right)+\left(-7\right)^2+\left(-7\right)^3+...+\left(-7\right)^{200}\)
  \(\Rightarrow\)                     \(\left(-7\right)A=\left(-7\right)^2+\left(-7\right)^3+\left(-7\right)^4+...+\left(-7\right)^{201}\)
  \(\Rightarrow\)\(A-\left(-7\right)A=8A=\left(-7\right)-\left(-7\right)^{201}\)
  \(\Rightarrow\)                                \(A=\frac{\left(-7\right)-\left(-7\right)^{201}}{8}=\frac{\left(-7\right)+7^{201}}{8}\)

A=(-7)+(-7)^2+...+(-7)^200

7a=-[7^2+7^3+...+7^201]

7a-a=-[(7^2+7^3+...+7^201)-(7+7^2+...+7^200)]

6a=-(7^2+7^3+...+7^201-7-7^2+...+7^200)

6a=-(7^201-7)

a=-\(\frac{-\left(7^{201}-7\right)}{6}\)

\(\frac{5}{6}\)

\(\sqrt{\frac{252525}{363636}}=\frac{5555}{6666}=\frac{5}{6}\)

Giúp mk vs mn ơi