giair pt sau : a) x+3=13-5x b) (5x-1) (5x-2)+3x(1-5x) = x² -1 c) 2x-1/2+x/3=3+4x/6-x+2

0 bình luận về “giair pt sau : a) x+3=13-5x b) (5x-1) (5x-2)+3x(1-5x) = x² -1 c) 2x-1/2+x/3=3+4x/6-x+2”

1. a) x+3=13-5x

   (=)x+3-13+5x=0

   (=)6x-10=0

   (=)6x=10

   (=)x=$\frac{5}{3}$ 

    S={$\frac{5}{3}$ }

   b) (5x-1) (5x-2)+3x(1-5x) = x² -1

   (=)(5x-1) (5x-2)+3x(1-5x) = (x-1)(x+1)

   (=)(5x-1)(5x-2)-3x(5x-1)=(x-1)(x+1)

   (=)(5x-1)(5x-2-3x)=(x-1)(x+1)

   (=)(5x-1)(2x-2)=(x-1)(x+1)

   (=)2(5x-1)(x-1)-(x-1)(x+1)=0

   (=)(5x-1)(x-1)-(x-1)(x+1)=0

   (=)(x-1)(5x-1-x-1)=0

   (=)(x-1)(4x-2)=0

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

   S={1;$\frac{5}{3}$}

   c) $\frac{2x-1}{2}$ +$\frac{x}{3}$ =$\frac{3+4x}{6}$ -x+2

   (=)$\frac{2x-1}{2}$ +$\frac{x}{3}$ -$\frac{3+4x}{6}$ +x-2=0

   (=)$\frac{3(2x-1)+2x-3-4x+6x-12}{6}$ =0

   (=)6x-3+2x-3-4x+6x-12=0

   (=)10x-18=0

   (=)10x=18

   (=)x=$\frac{9}{5}$ 

   S={$\frac{9}{5}$ }

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2. Đáp án:

    a)x+3=13-5x

   (=)6x=10

   (=)x=5/3

   S={5/3}

   b)(5x-1)(5x-2)+3x(1-5x)=x^2 -1

   c)2x-1/2+x/3=3+4x/6 -x+2

   (=)(2x-1).3/6+2x/6=3+4x/6+( 2-x).6/6

   (=)6x-3+2x=3+4x+12-6x

   (=)-2x=12

   (=)x=-6

   S={-6}

   Giải thích các bước giải:

    

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