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 7: Ta có: \(a\cdot b=ƯCLN\left(a;b\right)\cdot BCN\mathbb{N}\left(a;b\right)\)

=>\(a\cdot b=10\cdot900=9000\)

ƯCLN(a;b)=10

=>a⋮10; b⋮10

ab=9000

mà a⋮10 và b⋮10 và a<b

nên (a;b)∈{(10;900);(20;450);(30;300);(50;180);(60;150);(90;100)}

mà ƯCLN(a;b)=10

nên (a;b)∈{(10;900);(20;450);(50;180);(90;100)}

Bài 5:

ƯCLN(a;b)=6

=>a⋮6; b⋮6

ab=216

mà a⋮6; b⋮6

nên (a;b)∈{(6;36);(12;18);(18;12);(36;6)}

Bài 4: Gọi hai số tự nhiên cần tìm là a,b

ƯCLN(a;b)=5

=>a⋮5; b⋮5

Ta có: ab=300

mà a⋮5; b⋮5

nên (a;b)∈{(5;60);(60;5);(10;30);(30;10);(15;20);(20;15)}

Bài 1:

a: ƯCLN(a;b)=6

=>a⋮6 và b⋮6

a+b=96

mà a⋮6 và b⋮6

nên (a;b)∈{(6;90);(90;6);(12;84);(84;12);(18;78);(78;18);(24;72);(72;24);(30;66);(66;30);(36;60);(60;36);(42;54);(54;42);(48;48)}

mà ƯCLN(a;b)=6

nên (a;b)∈{(6;90);(90;6);(18;78);(78;18);(30;66);(66;30);(42;54);(54;42)}

b: ƯCLN(a;b)=4

=>a⋮4 và b⋮4

a+b=16

mà a⋮4; b⋮4 và a>b

nên (a;b)∈{(12;4);(8;8)}

mà ƯCLN(a;b)=4

nên (a;b)=(12;4)

ngón tay gầy

Trả lời gúp mình với p

d: \(48\cdot26+24\cdot148\)

\(=48\cdot26+48\cdot74\)

\(=48\cdot\left(26+74\right)=48\cdot100=4800\)

e: \(23\cdot48+92\cdot88\)

\(=23\cdot4\cdot12+92\cdot88\)

\(=92\cdot12+92\cdot88=92\cdot100=9200\)

b: \(89\cdot25+89\cdot74+89\)

\(=89\cdot\left(25+74+1\right)\)

\(=89\cdot100=8900\)