a: x-2 là ước của 2x+5

=>2x+5⋮x-2

=>2x-4+9⋮x-2

=>9⋮x-2

=>x-2∈{1;-1;3;-3;9;-9}

=>x∈{3;1;5;-1;11;-7}

b: 3x-5 là bội của x+1

=>3x-5⋮x+1

=>3x+3-8⋮x+1

=>-8⋮x+1

=>x+1∈{1;-1;2;-2;4;-4;8;-8}

=>x∈{0;-2;1;-3;3;-5;7;-9}

c: 5x+8⋮x+2

=>5x+10-2⋮x+2

=>-2⋮x+2

=>x+2∈{1;-1;2;-2}

=>x∈{-1;-3;0;-4}

d: 3x+1⋮2x-3

=>6x+2⋮2x-3

=>6x-9+11⋮2x-3

=>11⋮2x-3

=>2x-3∈{1;-1;11;-11}

=>2x∈{4;2;14;-8}

=>x∈{2;1;7;-4}

\(5^{2x+1}\cdot5^{2x+2}-5^x\cdot5^{3x+2}=100\)

\(\Leftrightarrow5^{4x+3}-5^{4x+2}=100\)

\(\Leftrightarrow625^x\left(5^3-5^2\right)=100\)

\(\Leftrightarrow625^x=1\)

hay x=0

\(\Rightarrow5^{2x+1+2x+2}-5^{x+3x+2}=100\\ \Rightarrow5^{4x+3}-5^{4x+2}=100\\ \Rightarrow5^{4x+2}\left(5-1\right)=100\\ \Rightarrow5^{4x+2}=25=5^2\\ \Rightarrow4x+2=2\Rightarrow x=0\)

Đáp án C

Đáp án B

5 3 x − 1 < 5 x + 3 ⇔ 5 x − 1 3 < 5 x + 3 ⇔ x − 1 3 < x + 3 ⇔ x > − 5

\(x.\left(53+42+5\right)=4.75\)

\(x.100=4.75\)

\(x=4.75.100\)

\(x=475\)

x.(53+42+5)=4.75

x.100=4.75

x=4.75x100

x=475

100 + x = 100 + 100 

100 + x = 200

x = 200 - 100 

x = 100

100+x=100+100

100+x=200

        x=200-100

        x=100

Vậy..

\(x^2=20x-100\)

\(\Leftrightarrow x^2-20x+100=0\)

\(\Leftrightarrow x-10=0\)

hay x=10

Ta có: \(A=2^0+2^1+2^2+\cdots+2^{100}\)

\(=1+\left(2^1+2^2\right)+\left(2^3+2^4\right)+\cdots+\left(2^{99}+2^{100}\right)\)

\(=1+2\left(1+2\right)+2^3\left(1+2\right)+\cdots+2^{99}\left(1+2\right)\)

\(=1+3\left(2+2^3+\cdots+2^{99}\right)\)

=>A chia 3 dư 1