1. Rút gọn biểu thức: a) 2x + (- 61) – (21 – 61); b) (- 3 – x + 5) + 3 c) 11 – (13 – x) + (13 – 11); d) 25 – (15 – x + 303) +303 2. Rút gọn biể

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1. 1. Rút gọn biểu thức:

   $a) 2x + (- 61) – (21 – 61)$

   $=2x-61-21+61$

   $=2x-21$

   $b) (- 3 – x + 5) + 3$

   $=-3-x+5+3$

   $=5-x$

   $c) 11 – (13 – x) + (13 – 11)$

   $=11-13+x+13-11$

   $=x$

   $d) 25 – (15 – x + 303) +303$

   $=25-15+x-303+303$

   $=10+x$

   2. Rút gọn biểu thức:

   $a) x + (-81) – ( 11 – 81)$

   $=x-81-11+81$

   $=x-11$

   $(-1 – x + 2) + 1$

   $=-1-x+2+1$

   $=-1+1+2-x$

   $=2-x$

   $c) 15 – ( 11 – x) + ( 11 – 15)$

   $=15-11+x+11-15$

   $=x$

   $15 – (15 – x + 202) + 202$

   $=15-15+x-202+202$

   $=x$

    

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2. 1.

    a, 2x + (-61) – (21-61)

     = 2x – 61 – 21 + 61

     = 2x + ( 61-61) -21

     = 2x -21

    b, (-3 – x + 5 ) +3

     = -3 – x + 5 + 3

     = ( -3 + 3 ) + 5 – x

     = 5 – x

   2.

    a, x + (-81) – ( 11 – 81)

    = x – 81 – 11 + 81

    = x -11 + ( 81 – 81)

    = x – 11

   b, ( -1 – x + 2 ) + 1

    = -1 – x + 2 + 1

    = ( -1 + 1) + 2 – x

    = 2 – x

    c, 15 – (11 -x) + (11 – 15)

    = 15 – 11 + x + 11 – 15

    = ( 15 -15 ) + (11 -11) + x

    = x

    d, 15 – (15 – x + 202) + 202

    = 15 – 15 + x – 202 + 202

    = (15 -15) + (202 – 202) + x

    = x

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