2/5.3x-1/2-1/4=1/5

=>2/5.3x-1/4=1/5

=>2/5.3x=1/5+1/4

=>2/5.3x=9/20

=>3.x=9/20:2/5

=>3.x=9/8

=>x=9/8:3

=>x=3/8

vay x=3/8

2/5.3x-1/2-1/4 = 1/5

=> 2/5.3x = 1/5+1/4+1/2

2/5.3x = 19/20

3x = (19/20):(2/5)

3x = 19/8

x = (19/8):3

x = 19/24 

\(a,5^x+5^{x+2}=650\\ \Rightarrow a,5^x+5^x.25=650\\ \Rightarrow26.5^x=650\\ \Rightarrow5^x=25\\ \Rightarrow5^x=5^2\\ \Rightarrow x=2\)

\(b,3^{x.1}+5.3^{x.1}=162\\ \Rightarrow3^x+5.3^x=162\\ \Rightarrow6.3^x=162\\ \Rightarrow3^x=27\\ \Rightarrow3^x=3^3\\ \Rightarrow x=3\)

a: \(\Leftrightarrow5^x=25\)

hay x=2

a, <=> 5^x + 5^x .5² =650

<=> 5^x +25.5^x =650

<=> 26.5^x =650

<=> 5^x =25

<=> 5^x = 5²

<=> x=2

b, <=> 6. 3^x =162

 <=> 3^x =27

<=> 3^x =3³

<=> x=3

Chúc bạn học tốt nha!

Trả lời:

\(3x+1+5\times3x+2=144\)

\(\Leftrightarrow3x+1+15x+2=144\)

\(\Leftrightarrow18x=141\)

\(\Leftrightarrow x=\frac{47}{8}\)

Vậy \(x=\frac{47}{8}\)

chờ chút

mà 3x+2 là riêng x thôi hay cả 3x ậy bạn

theo tớ là riêng x thôi. mà đề bài là dấu cộng mà.

x = 2

\(3^{x+2}-5.3^x=36\)

\(\Leftrightarrow3^x.9-5.3^x=36\)

\(\Leftrightarrow3^x\left(9-5\right)=36\)

\(\Leftrightarrow3^x.4=36\Leftrightarrow3^x=9\Leftrightarrow x=2\)

Đáp án D.

\(B=5\cdot\left(2x-1\right)^2+4\cdot\left(x-1\right)\cdot\left(x+3\right)-2\cdot\left(5\cdot3x\right)\)

\(=5\left(4x^2-4x+1\right)+\left(4x-4\right)\cdot\left(x+3\right)-2\cdot15x\)

\(=20x^2-20x+5+4x^2+12x-4x-12-2\cdot15x\)

\(=20x^2-20x+5+4x^2+12x-4x+12-30x\)

\(=24x^2-42x-7\)

(B=5left(2x-1 ight)^2+4left(x-1 ight)left(x+3 ight)-2left(5.3x ight)=5left(4x^2-4x+1 ight)+4left(x^2-4x+3 ight)-30x=20x^2-20x+5+4x^2-16x+12-30x=24x^2-66x+17)

\(B=5.\left(2x-1\right)^2+4\left(x-1\right)\left(x+3\right)-2\left(5.3x\right)\)

\(B=5\left(4x^2-4x-1\right)+4\left(x^2+3x-x-3\right)-30x\)

\(B=20x^2-20x-5+4x^2+8x-12-30x\)

\(B=24x^2-2x-17\)

Chúc bạn học tốt!!!

Ta có: \(4.3^{x+2}-2.3^{x+1}=810\)

\(4.3^{x+1}.3-2.3^{x+1}=810\)

\(2.3^{x+1}\left(2.3-1\right)=810\)

\(2.3^{x+1}.5=810\)

\(3^{x+1}=81=3^4\)

x+1=4

x=3

Nguyễn Thị Mai:

\(^{\frac{1}{2.3}x+\frac{1}{3.4}x+....+\frac{1}{49.50}x=1}\)

Đặt: \(^{\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\right)x=1}\)

\(^{\Leftrightarrow\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\right)x=1}\)

\(^{\Leftrightarrow\frac{1}{2}+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+...+\left(\frac{1}{49}-\frac{1}{49}\right)-\frac{1}{50}x=1}\)

\(^{\Leftrightarrow\left(\frac{1}{2}+0+0+...+0-\frac{1}{50}\right)x=1}\)

\(^{\Leftrightarrow\left(\frac{1}{2}-\frac{1}{50}\right)x=1}\)

\(^{\Leftrightarrow\frac{12}{25}x=1}\)

\(^{\Leftrightarrow x=\frac{25}{12}}\)

Tham khảo nha ~~