a, (-2)×(-7)×(-5)+(-5)×(-6) b, (-7)×2×(-5)-8×(-3)² c, 700-(-200)-300-100 d,175-(-25)-(-3)³+(-38+40)×(-2) e, (-3)×x+12=21 g, 5

1 bình luận về “a, (-2)×(-7)×(-5)+(-5)×(-6) b, (-7)×2×(-5)-8×(-3)² c, 700-(-200)-300-100 d,175-(-25)-(-3)³+(-38+40)×(-2) e, (-3)×x+12=21 g, 5”

1. a =14×(-5)+30=-70+30=40

   b =-14×(-5)-8×9=70-72=-2

   c =700+200-300-100=900-300-100=500

   d =175+25+27+2×(-2)=227+(-4)=223

   e =-3×x=21-12

         -3×x=9

         x=9:(-3)

         X=-3

   g =x+7=15:5

        x+7=3

        x=3-7

        x=-4

   h =2×x+14=-24

         2×x=-24-14

         2×x=-38

         x=-38:2 

         x=-19

   i =2×(x+6)=37-29

        2×(x+6)=8

        x+6=8:2=4

        x=4-6

        x=-2

   thêm 

   a⇒x+7=0 hoặc x-5=0

   TH1 x+7=0

         ⇒x=-7

   TH2 x-5=0

   ⇒x=5

   b =2×(x-6)^2=49+1=50

   (x-6)^2=50:2=25

   ⇒(x-6)^2=5^2

   ⇒x-6=5

   x=5+6 

   x=11

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