Bài 1:

a: 2x+3=15

=>2x=15-3=12

=>\(x=\frac{12}{2}=6\)

b: 28-3x=13

=>\(3x=28-13=15\)

=>\(x=\frac{15}{3}=5\)

c: \(\left(x-1954\right)\cdot5=50\)

=>x-1954=50:5=10

=>x=10+1954=1964

d: 30(60-x)=30

=>60-x=1

=>x=60-1=59

Bài 2:

a: x+99:3=55

=>x+33=55

=>x=55-33=22

b: (x-25):15=20

=>\(x-25=20\cdot15=300\)

=>x=300+25=325

c: \(7\left(3x-15\right)=42\)

=>\(3x-15=\frac{42}{7}=6\)

=>3x=15+6=21

=>\(x=\frac{21}{3}=7\)

d: \(x\left(x+1\right)=2+4+6+\cdots+2500\)

=>\(x\left(x+1\right)=2\left(1+2+3+\cdots+1250\right)\)

=>\(x\left(x+1\right)=2\cdot1250\cdot\frac{1251}{2}=1250\cdot1251\)

=>\(x^2+x-1250\cdot1251=0\)

=>(x+1251)(x-1250)=0

=>\(\left[\begin{array}{l}x+1251=0\\ x-1250=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=-1251\\ x=1250\end{array}\right.\)

Bài 1:

a: \(46\cdot99=46\cdot\left(100-1\right)=46\cdot100-46\)

=4600-46

=4554

b: \(47\cdot98=47\cdot\left(100-2\right)=47\cdot100-47\cdot2\)

=4700-94

=4604

c: \(18\cdot19=18\left(20-1\right)=18\cdot20-18\)

=360-18

=342

d: \(24\cdot198=24\left(200-2\right)\)

\(=24\cdot200-24\cdot2\)

=4800-48

=4752

Bài 2:

a: \(1800\cdot5=18\cdot100\cdot5=90\cdot100=9000\)

b: \(36\cdot25=25\cdot4\cdot9=100\cdot9=900\)

c: 36600:50=3660:5=732

d: 220000:5000=220:5=44

sạc xong rồi học đk

\(1,2^3-5^3:5^2+12\cdot2^2\)

\(=8-5+12\cdot4=3+48=51\)

\(2)5\cdot\left\lbrack\left(85-35:7\right):8+90\right\rbrack-50\)

\(=5\cdot\left\lbrack\left(85-5\right):8+90\right\rbrack-50\)

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

\(=5\cdot\left(10+90\right)-50=5\cdot100-50\)

\(=500-50=450\)

\(3)2\cdot\left\lbrack\left(7-3^3:3^2\right):2^2+99\right\rbrack-100\)

\(=2\cdot\left\lbrack\left(7-3\right):4+99\right\rbrack-100\)

\(=2\cdot\left(1+99\right)-100=2\cdot100-100\)

\(=200-100=100\)

\(4)2^7:2^2+5^4:5^3\cdot2^4-3\cdot2^5\)

\(=2^5+5^2\cdot16-3\cdot32=32+25\cdot16-96\)

\(=32+400-96=336\)

\(5)5\cdot2^2\cdot2^3-4\cdot\left(5^8:5^6\right)=5\cdot2^5-4\cdot5^2\)

\(=5\cdot32-4\cdot25=160-100=60\)

\(6)\left(3^5\cdot3^7\right):3^{10}+5\cdot2^4-7^3:7\)

\(=3^{12}:3^{10}+5\cdot16-7^2=9+80-49=40\)

\(7)15:\left(3^5:3^4\right)-2^9:2^7\)

\(=15:3-4=5-4=1\)

\(8)5\cdot3^5:\left(3^8:3^5\right)-2^3\cdot5\)

\(=5\cdot3^2-40=5\cdot9-40=45-40=5\)

\(9)4\left\lbrack\left(3+3^7:3^4\right):10+97\right\rbrack-300\)

\(=4\left\lbrack\left(3+3^3\right):10+97\right\rbrack-300\)

\(=4\left\lbrack\left(3+27\right):10+97\right\rbrack-300\)

\(=4\cdot\left(3+97\right)-300=400-300=100\)

\(10)5\left\lbrack\left(92+2^5:2^2\right):5^2+2^4\right\rbrack-7^2\)

\(=5\left\lbrack\left(92+8\right):25+16\right\rbrack-49\)

\(=5\cdot\left(100:25+16\right)-49\)

\(=5\cdot\left(4+16\right)-49=100-49=51\)

\(11)3^2\cdot\left\lbrack5^2-3\right):11]-2^4+2\cdot10^3\)

\(=9\cdot\left(22:11\right)-16+2000=9\cdot2-16+2000\)

\(=18-16+2000=2002\)

\(12)2^2\cdot5\left\lbrack\left(5^2+2^3\right):11-2\right\rbrack-3^2\cdot2\)

\(=4\cdot5\left\lbrack\left(25+8\right):11-2\right\rbrack-18\)

\(=20\cdot\left(3-2\right)-18=20-18=2\)

\(13)\left(6^{2007}-6^{2006}\right):6^{2006}\)

\(=\left\lbrack6^{2006}\cdot\left(6-1\right)\right\rbrack:6^{2006}=5\)

14) \(\left(5^{2001}-5^{2000}\right):5^{2000}\)

\(=\left\lbrack5^{2000}\cdot\left(5-1\right)\right\rbrack:5^{2000}=4\)

\(15)\left(7^{2005}+7^{2004}\right):7^{2004}\)

\(=\left\lbrack7^{2004}\cdot\left(7+1\right)\right\rbrack:7^{2004}=8\)

\(16)\left(11^{2023}+11_{}^{2022}\right):11^{2022}\)

\(=\left\lbrack11^{2022}\cdot\left(11+1\right)\right\rbrack:11^{2022}=12\)

10 cách

Gọi tổng chi phí cho chuyến đi là x(đồng)

(Điều kiện: x>0)

Số tiền mỗi bạn phải đóng ban đầu là \(\frac{x}{40}\) (đồng)

Số tiền mỗi bạn phải đóng thực tế là \(\frac{x}{36}\) (đồng)

Mỗi bạn tham gia còn lại phải đóng thêm 25000 đồng nên ta có:

\(\frac{x}{36}-\frac{x}{40}=25000\)

=>\(\frac{x}{360}=25000\)

=>\(x=25000\cdot360=9000000\) (đồng)

vậy: Tổng chi phí cho chuyến đi là 9000000(đồng)

Bài 5:

a: \(B=2009\cdot2011\)

\(=\left(2010-1\right)\left(2010+1\right)\)

\(=2010\cdot2010-1=A-1\)

=>B<A
b: \(B=2019\cdot2021\)

\(=\left(2020-1\right)\left(2020+1\right)\)

\(=2020\cdot2020-1\)

=A-1

=>B<A

c: \(A=234234\cdot233=234\cdot233\cdot1001\)

\(B=233233\cdot234=233\cdot234\cdot1001\)

Do đó: A=B

d: \(A=123\cdot137137=123\cdot137\cdot1001\)

\(B=137\cdot123123=137\cdot123\cdot1001\)

Do đó: A=B

Bài 4:

a: \(391-125<\overline{26x}<184+84\)

=>\(266<\overline{26x}<268\)

=>\(\overline{26x}=267\)

=>x=7

b: \(935+167<\overline{110x}<1240-135\)

=>\(1102<\overline{110x}<1105\)

=>x∈{3;4}

c: \(135\cdot12<\overline{162x}<4869:3\)

=>\(1620<\overline{162x}<1623\)

=>x∈{1;2}

d: \(11268:3<\overline{375x}<235\cdot16\)

=>\(3756<\overline{375x}<3760\)

=>x∈{7;8;9}

Bài 3:

l: x+125=492

=>x=492-125=367

m: 327-x=129

=>x=327-129=198

n: 124+(118-x)=217

=>118-x=217-124=93

=>x=118-93=25

o: 89-(73-x)=20

=>73-x=89-20=69

=>x=73-69=4

p: 198-(x+4)=120

=>x+4=198-120=78

=>x=78-4=74

q: (x+7)-25=23

=>x+7=25+23=48

=>x=48-7=41

r: 140:(x-8)=7

=>x-8=140:7=20

=>x=20+8=28

s: 4(x+41)=400

=>x+41=400:4=100

=>x=100-41=59

t: 4(3x-4)-2=18

=>4(3x-4)=2+18=20

=>3x-4=5

=>3x=9

=>x=3

u: 123-5(x+4)=38

=>5(x+4)=123-38=85

=>x+4=85:5=17

=>x=17-4=13

v: 231-(x-6)=1339:13

=>231-(x-6)=103

=>x-6=231-103=128

=>x=128+6=134

w: (x-36):18+12=14

=>(x-36):18=2

=>\(x-36=2\cdot18=36\)

=>x=36+36=72