1,tính C= 3^4 + (-3)^5+…….+ (-3) ^201 2 tìm x a, ( x-3) ^206 =/x-3/ b, ( x-2) ( 2x -10) = 0

Đáp án:

`1.  ((-3)^(201)-81)/(-4)`

`2. a)` \(\left[ \begin{array}{l}x=3\\x=4\end{array} \right.\)

`b) `\(\left[ \begin{array}{l}x=2\\x=5\end{array} \right.\)

Giải thích các bước giải:

`C=3^4+(-3)^5+…+(-3)^(201)`

`C=(-3)^4+ (-3)^5+…+(-3)^(201)`

`(-3).C=(-3)^5+(-3)^6+…+(-3)^(201)`

`(-3).C-C=[(-3)^5+(-3)^6+…+(-3)^(201)]-[(-3)^4+ (-3)^5+…+(-3)^(201)]`

`(-4).C=(-3)^(201)-81`

`C=((-3)^(201)-81)/(-4)`

`2)`

`a) (x-3)^(206)=|x-3|`

`=> (x-3)^(206)-|x-3|=0`

`=> (x-3)[(x-3)^(205)-1]=0`

`=>` \(\left[ \begin{array}{l}x-3=0\\(x-3)^(205)-1=0\end{array} \right.\) 

`=>` \(\left[ \begin{array}{l}x=3\\(x-3)^(205)=1\end{array} \right.\) 

`=>` \(\left[ \begin{array}{l}x=3\\x-3=1\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}x=3\\x=4\end{array} \right.\)

`b) (x-2)(2x-10)=0`

`=>` \(\left[ \begin{array}{l}x-2=0\\2x-10=0\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}x=2\\x=5\end{array} \right.\)