1)5^x+1 + 6.5^x+1 = 875

   5^x+1 ( 1+6 ) = 875

   5^x+1 . 7 = 875

5^x+1 = 875 : 7

5^x+1 = 125

5^x+1 = 5³

x+1 = 3

x = 3 - 1

x = 2

2)3^x+1 + 3^x+3 = 810

  3^x . 3 + 3² . 3^x+1 = 810

  3^x . 3 + 9 . 3^x . 3 = 810

  3^x .3 ( 1 + 9 ) = 810

  3^x+1 . 10 = 810

  3^x+1 = 810 : 10

  3^x+1 = 81

  3^x+1 = 3⁴ 

x+1 = 4

x = 4-1

x = 3

1. 15^x=225

   <=>15^x=15^2

    =>x=2

    vậy....

2. x^3=27

   <=>x^3=3^3

   =>x=3

vậy......

3. 4.2^x-3=125

   4.2^x=128

   2^x=32

   2^x=2^5

   =>x=5

vậy.....

\(15^x=225\)

\(\Leftrightarrow15^x=15^2\)

\(\Leftrightarrow x=2\)

\(x^3=27\)

\(\Leftrightarrow x^3=3^3\)

\(\Leftrightarrow x=3\)

\(4.2^x-3=125\)

\(\Leftrightarrow4.2^x=125+3\)

\(\Leftrightarrow4.2^x=128\)

\(\Leftrightarrow2^x=128:4\)

\(\Leftrightarrow2^x=32\)

\(\Leftrightarrow2^x=2^5\)

\(\Leftrightarrow x=5\)

~ Hok tốt ~

Bạn đợi tí nha Trần Phương Thùy

Mình đang trả lời !

\(a,\text{ }3^{x+4}-3^x=6480\)

\(3^x\left(3^4-1\right)=6480\)

\(3^x\cdot80=6480\)

\(3^x=6480\text{ : }80\)

\(3^x=81\)

\(3^x=3^4\)

\(\Rightarrow\text{ }x=4\)

\(b,\text{ }x^5=4x^3\)

\(x^5-4x^3=0\)

\(x^3\left(x^2-4\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x^3=0\\x^2-4=0\end{cases}}\)                    \(\Rightarrow\orbr{\begin{cases}x=0\\x^2=4\end{cases}}\)               \(\Rightarrow\orbr{\begin{cases}x=0\\x=\pm2\end{cases}}\)

                   \(\Rightarrow\text{ }x\in\left\{0\text{ ; }-2\text{ ; }2\right\}\)

thì cũng là :
(x+3)^2
(x-5y)^2
(3x-2y)^2
mình chưa hiểu lắm

\(\left(x+3\right)^2=x^2+6x+9\)

\(\left(x-5y\right)^2=x^2-10xy+25y^2\)

\(\left(3x-2y\right)^2=9x^2-12xy+4y^2\)

1 ) 3yx - 6xy² 

= 3xy ( 1 - 2y )

2 ) 5ab² - 20a³b²

= 5ab² ( 1 - 4a² )

= 5ab² ( 1 - 2a ) ( 1 + 2a )

3 ) 3x - 3b - y ( b - x )

= 3 ( x - b ) + y ( x - b )

= ( x - b ) ( 3 + y ) 

1)3xy-6xy²=3xy(1-2y)

2)5ab²-20a³b²=5ab²(1-4a²)=5ab²[1²-(2a)²]=5ab²(1+2a)(1-2a)

3)3x-3b-y(b-x)=3x-3b-by+xy=(3x+xy)-(3b+by)=3x(1+y)-3b(1+y)=3(1+y)(x-b)

\(3xy-6\left(xy\right)^2=3xy.\left(1-2xy\right)\)

\(5\left(ab\right)^2-20a^3b^2=5a^2b^2\left(1-4a\right)\)

\(3x-3b-y\left(b-x\right)=3.\left(x-b\right)+y.\left(x-b\right)=\left(x-b\right)\left(3+y\right)\)

Động não chút~

so cac so mu la (99 -1) : 1+1= 99 so 

tong cac so mu la (99+1) x 99 : 2 =4950

=> =3⁴⁹⁵⁰ =..............................

ban tu tinh lam bieng rut gon qua ban thich rut thi rut tuy co ban

= 3 mũ ( 99 +1 ) .(99 - 1) : 2 + 1

= 3 mũ 4901