## câu 1: a) -50+20 b)-30-10 c)-55+(-20) d) -99 +100-1+99 câu 2: Bỏ ngoặc

Question

câu 1: a) -50+20 b)-30-10 c)-55+(-20) d) -99 +100-1+99 câu 2: Bỏ ngoặc rùi tính a)-50-[-30-(20-30)-50] b) 25 +(30-25)-30 câu 3: tìm x a) 25+x =30-(-15) b) x+20 =-50 +25

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3 tuần 2021-11-17T00:16:15+00:00 2 Answers 3 views 0

## Answers ( )

1. câu 1

a) -50+20=-30

b)-30-10=-40

c)-55+(-20)=-75

d)-99+100-1+99=(-99+99)+(100-1)=0+99=99

câu 2

a)-50-[-30-(20-30)-50]

=50-(-30)-20+30-50

=80-20+30-50

=60+30-50

=90-50

=40

b)25+(30-25)-30

=25+30-25-30

=(25-25)+(30-30)

=0+0=0

câu 3

a)25+x=30-(-15)

25+x=45

x=45-25

x=20

b)x+20=-50+25

x+20=-25

x=-25-20

x=-45

2. câu 1 :

a) -50+20

= – ( 50 – 20 )

= – 30

b) – 30 – 10

= ( – 30 ) + ( -10 )

= -40

c) – 55 + ( – 20 )

= – 75

d) -99 +100-1+99

= ( – 99 + 99 ) + ( 100 – 1 )

=   0 + 99

= 99

câu 2 :

a)- 50 – [ – 30 – ( 20 – 30 ) – 50 ]

= – 50 + 30 + ( 20 – 30 ) + 50

= -50 + 30 +  20 – 30  + 50

= ( -50 + 50 ) + ( 30 – 30 ) + 20

= 20

b) 25 + ( 30 – 25 ) – 30

= 25 + 30 – 25 – 30

= ( 25 – 25 ) + ( 30 – 30 )

= 0

câu 3 :

a) 25 + x = 30  – ( – 15 )

25 + x = 30 + 15

25 + x = 45

x = 45 – 25

x = 20

b) x + 20 = -50 + 25

x + 20 = – 25

x          = -25 – 20

x          = – 45