a. (x-2)*(x+1/4)=0 b.x+2*x+3*x+…….+100*x=5050

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1. Đáp án:

   a.$x\in\{2,\dfrac{-1}{4}\}$

   b.$x=1$

   Giải thích các bước giải:

   a.$(x-2)(x+\dfrac{1}{4})=0$

   $\rightarrow x-2=0\rightarrow x=2$

   Hoặc $x+\dfrac{1}{4}=0\rightarrow x=\dfrac{-1}{4}$

   b.$x+2x+3x+..+100x=5050$

   $\rightarrow x(1+2+3+..+100)=5050$

   $\rightarrow x.((1+100).100:2)=5050$

   $\rightarrow x.5050=5050$

   $\rightarrow x=1$

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2. $a,(x-2)(x+\dfrac{1}{4})=0$

   \(⇒\left[ \begin{array}{l}x-2=0⇒x=2\\x+\dfrac{1}{4}=0⇒x=-\dfrac{1}{4}\end{array} \right.\)

   $b,x+2x+3x+…+100x=5050$

   $⇒x(1+2+3+…+100)=5050$

   $⇒5050x=5050$

   $⇒x=1$

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