Bài 2 Tìm x: a) 27-(27-x)=45 ,
27+x-27=45
x=45
b) -18+42=42-2x
24=42-2x
2x=42-14
2x=28
x=14
1)
a) (-38).47+147.38
= 38.(147 - 47)
= 38 . 100 = 3800
b) 37.42-142.37+15
= 37.(42 - 142) + 15
= 37. (-100) + 15
= -3700 + 15 = -3685
c) 46.115-14.46+(-46)
= 46.(115 - 14 - 1)
= 46 . 100 = 4600
2)
a) 27-(27-x) = 45
27-x = 27 - 45
27-x = -18
x = 27 + 18
=> x = 45
Vậy x = 45
b) -18+42=42-2x
2x = 42 + 18 - 42
2x = 18
=> x = 9
Vậy x = 9
Chúc em học tốt!!!
bài 1
a -38.47+147.38
= -38.47+147.-1.-38
=-38.47+-147.-38
=-38.(47+-147)
= -38.-100
=3800
b, 37.42-142.37+15
= 37(42-142)+15
=37.-100+15
=-3700+15
=3715
c, 46.115-14.46+ -46
= -46.-1.115-14.-46.-1+ -46.1
=-46(115-14+1)
=46.102
=4692
bài 2
27-(27-x)=45
27-x=27-45
27-x= -18
x=27+18
x=45
b, -18+42=42-2x
24=42-2x
hay42-2x=24
2x=42-24
2x=18
x=18:2
x=9
1)
a) (-38).47+147.38
= 38.(147 - 47)
= 38 . 100 = 3800
b) 37.42-142.37+15
= 37.(42 - 142) + 15
= 37. (-100) + 15
= -3700 + 15 = -3685
c) 46.115-14.46+(-46)
= 46.(115 - 14 - 1)
= 46 . 100 = 4600
2)
a) 27-(27-x) = 45
27-x = 27 - 45
27-x = -18
x = 27 + 18
=> x = 45
Vậy x = 45
b) -18+42=42-2x
2x = 42 + 18 - 42
2x = 18
=> x = 9
Vậy x = 9