5 . [(85 - 35 : 7) : 80 + 90] - 50
= 5 . [(85 - 5) : 80 + 90] - 50
= 5 . [80 : 80 +90] - 50
= 5 . [1 + 90] - 50
= 5 . 91 - 50
= 455 - 50 = 405

5 [ ( 85 - 35 : 7 ) : 80 + 90 ] - 50

= 5 [ ( 85 - 5 ) : 80 + 90 ] - 50

= 5 [ 80 : 80 + 90 ] - 50

= 5 [ 1 + 90 ] - 50

= 5 . 91 - 50

= 455 - 50

= 405

=))

5 x [(85 - 35 : 7) : 8 + 90] - 50

= 5 x [(85 - 5) : 8 + 90] - 50

= 5 x [80 : 8 + 90] - 50

= 5 x [10 + 90] - 50

= 5 x 100 - 50

= 500 - 50

= 450

\(5\times\left[\left(85-35:7\right):8+90\right]-50\\ =5\times\left[\left(85-5\right):8+90\right]-50\\ =5\times\left[80:8+90\right]-50\\ =5\times\left[10+90\right]-50\\ =5\times100-50\\ =500-50=450\)

5[(85 - 35 : 7) : 8 + 90] - 50

= 5[(85 - 5) : 8 + 90] -  50

= 5.[ 80 : 8 + 90] - 50

= 5.[ 10 + 90 ] - 50

= 5. 100 - 50

= 500 - 50

= 450

5[(85 - 35 : 7) : 8 + 90] - 50

= 5[(85 - 5) : 8 + 90] -  50

= 5.[ 80 : 8 + 90] - 50

= 5.[ 10 + 90 ] - 50

= 5. 100 - 50

= 500 - 50

= 450

a) 2³.15 -[115-(12-5)² ]

= 2³.15 -[115-36]

= 8.15 -79

= 120-79

=41

b)5.[(85 - 35 : 7) :8 + 90 ] - 50

=5 .[80:8+90]-50

=5.100-50

=500-50

=450

c){[261 - ( 36-31)³.2 ]-9}.1001

={[261 - 125.2 ]-9}.1001

={[261 -250 ]-9}.1001

={11-9}.1001

=2.1001

=2002

d)3.10² - [1200 - ( 4² - 2.3)^3]

=3.100-[1200 -(16-6)³ ]

=300-[1200-1000]

=300-200

=100

\(a)2^3\cdot15-[115-(12-5)^2]\\=8\cdot15-(115-7^2)\\=120-(115-49)\\=120-66\\=54\\---\\b)5\cdot[(85-35:7):8+90]-60\\=5\cdot[(85-5):8+90]-60\\=5\cdot(80:8+90)-60\\=5\cdot(10+90)-60\\=5\cdot100-60\\=500-60\\=440\)

\(---\)

\(c,\left\{\left[261-\left(36-31\right)^3\cdot2\right]-9\right\}\cdot1001\)

\(=\left[\left(261-5^3\cdot2\right)-9\right]\cdot1001\)

\(=\left[\left(261-125\cdot2\right)-9\right]\cdot1001\)

\(=\left[\left(261-250\right)-9\right]\cdot1001\)

\(=\left(11-9\right)\cdot1001\)

\(=2\cdot1001\)

\(=2002\)

\(---\)

\(d,3\cdot10^2-\left[1200-\left(4^2-2\cdot3\right)^3\right]\)

\(=3\cdot100-\left[1200-\left(16-6\right)^3\right]\)

\(=300-\left(1200-10^3\right)\)

\(=300-\left(1200-1000\right)\)

\(=300-200\)

\(=100\)

#\(Toru\)

85+(-35)+(-12)+(-35)=50+(-12)+(-35)=38+(-35)=3
5³.4²+85.5³-5⁷:5⁴=125.16+85.125-5³=125.16+85.125-125
=125.16+85.125-125.1=(16+85-1).125=100.125=12500
 

\(5.\left[\left(85-35:7\right):8+90\right]\)

\(=5.\left[\left(85-5\right):8+90\right]\)

\(=5.\left(80:8+90\right)\)

\(=5.\left(10+90\right)\)

\(=5.100\)

\(=500\)

\(5\left[\left(85-35:7\right):8+90\right]\)

\(=5\left[\left(85-5\right):8=90\right]-50\)

\(=5\left[80:8+90\right]-50\)

\(=5\left[10+90\right]-50\)

\(=5.100-50\)

\(=450\)

\(2^3-5^3:5^2+12\cdot2^2=8-5+48=51\\ 5\left[\left(85-35:7\right):8+90\right]-5\cdot2^2\\ =5\left(80:8+90\right)-20=5\cdot100-20=480\)

a: \(2^3-5^3:5^2+12\cdot2^2\)

\(=8-5+48\)

\(=51\)

b: \(5\cdot\left[\left(85-35:7\right):8+90\right]-5\)

\(=5\cdot\left[10+90\right]-5\)

=495

a: 23−53:52+12⋅2223−53:52+12⋅22

=8−5+48=8−5+48

=51=51

b: 5⋅[(85−35:7):8+90]−55⋅[(85−35:7):8+90]−5

=5⋅[10+90]−5=5⋅[10+90]−5

=495

Bài 1:

a: 212+109+188

=212+188+109

=400+109

=509

b: 305+295+140

=600+140

=740

c: \(9\cdot4\cdot25\cdot8\cdot125\)

\(=9\cdot100\cdot1000\)

=900000

d: 35+56+65+44

=35+65+56+44

=100+100

=200

e: 277+194+206+123

=277+123+194+206

=400+400

=800

g: \(8\cdot25\cdot2\cdot4\cdot5\cdot125\)

\(=2\cdot5\cdot4\cdot25\cdot8\cdot125\)

\(=10\cdot100\cdot1000=1000000\)

h: \(29\cdot25+29\cdot45+29\cdot30\)

\(=29\left(25+45+30\right)=29\cdot100=2900\)

i: \(36\left(143+57\right)+64\left(143+57\right)\)

\(=36\cdot200+64\cdot200\)

\(=200\left(36+64\right)=200\cdot100=20000\)

k: \(491\cdot\left(747+53\right)+491\left(153+47\right)\)

\(=491\left(747+153+53+47\right)\)

\(=491\left(900+100\right)=491\cdot1000=491000\)

Bài 4:

a: M=1+2+3+...+103

\(=\frac{103\left(103+1\right)}{2}=103\cdot\frac{104}{2}=103\cdot52=5356\)

b: Số số hạng của dãy là (99-3):4+1=96:4+1=24+1=25(số)

Tổng của dãy số là:

\(N=\left(99+3\right)\cdot\frac{25}{2}=51\cdot25=1275\)

c: Số số hạng của dãy là:

(991-1):10+1=990:10+1=99+1=100(số)

Tổng của dãy số là:

\(C=\left(991+1\right)\cdot\frac{100}{2}=992\cdot50=49600\)