Bài 4:
a.325+138+12+25
=(325+15)+(138+12)
=340+150
=490
b.36x372+63 x372+372
=372x(36+63+1)
=372 x100
=37200
c.53 x11
=53x(10+1)
=530+53
=583
d.12x25+29x25+59x25
=25x(12+29+59)
=25x100
=2500
b.135+360+65+40
=(135+65)+(360+40)
=200+400
=600
d.79x101
=79x(100+1)
=7900+79
=7979
e.19x25x2x5x4
=(25x4)x(2x5)x19
=100x10x19
=19000
f.28x(231+69)+72x(231+69)
=28x100+72x100
=100x(28+72)
=100x100
=10000
Bài5:
a.x+17=27
⇔x=27-17
⇔x=10
b.x :17=3
⇔x=17x3
⇔x=51
c.(x-7).(x-11)=0
⇔x-7=0 ⇔x=7
x-11=0 x=11
d.30 .(x-6)=30
⇔x-6=30:30
⇔x-6=1
⇔x=1+6
⇔x=7
e.(x-105) :21=15
⇔x-105=15 .21
⇔x-105=315
⇔x=315+105
⇔x=420
d.x+324=500
⇔x=500-324
⇔x=176
e.(x-11)+37=117
⇔x-11=117-37
⇔x-11=80
⇔x=80+11
⇔x=91
f.x+4x=150
⇔5x=150
⇔x=150 :5
⇔x=10
c.315+(125-x)=435
⇔315+125-x=435
⇔440-x=435
⇔x=440-435
⇔x=5
d.(x-5).(x-7)=0
⇔x-5=0 ⇔x=5
x-7=0 x=7
.................................................chúc bn hk tốt.................................
