$a,$

$2^{20}.15+2^{10}.85$

$=2^{20}.2^{10}.85+15$

$=2^{30}.100$

$=2^{30}{.10}^2$    

$b,$

${27}^{16}:9^{10}$

$=(3^3{)}^{16}:(3^2{)}^{1}0$

$=3^{48}:3^{20}$

$=3^{28}$ 

$c,$ 

${125}^3:{25}^4$

$=(5^3{)}^5:(5^{}$

mong cac ban tra loi chu minh cung muon tim ket qua cua cau nay lam

a, \(390-\left(x-7\right)=13^2:12\)

\(390-\left(x-7\right)=\) \(\dfrac{169}{12}\)

\(x-7=390-\dfrac{169}{12}\)

\(x-7=\dfrac{4511}{12}\)

\(x=\dfrac{4511}{12}+7\)

\(x=\dfrac{4595}{12}\)

Vậy ...

b, \(\left(x-35.2^2\right):7=3^3-24\)

\(\left(x-35.4\right):7=27-24\)

\(\left(x-140\right):7=3\)

\(\Leftrightarrow\left(x-140\right)=3.7\)

\(\Leftrightarrow x-140=21\)

\(\Leftrightarrow x=161\)

Vậy .....

c) \(x-6:2-\left(4^2.3-24\right):2:6=3\)

\(x-3-\left(16.3-24\right):2:6=3\)

\(x-3-\left(48-24\right):2:6=3\)

\(x-3-24:2:6=3\)

\(x-3-2=3\)

\(x=3+2+3\)

\(x=8\)

Vậy ......

d) \(4x-5=5+5^2+5^3+.....+5^{99}\)

Đặt :

\(A=5+5^2+.........+5^{99}\)

\(\Leftrightarrow5A=5^2+5^3+..........+5^{100}\)

\(\Leftrightarrow5A-A=\left(5^2+5^3+......+5^{100}\right)-\left(5+5^2+....+5^{99}\right)\)

\(\Leftrightarrow4A=5^{100}-5\)

\(\Leftrightarrow A=\dfrac{5^{100}-5}{4}\)

\(\Leftrightarrow4x+5=\dfrac{5^{100}-5}{4}\)

Đến đây thì sao nữa nhỉ ?

e) \(\left(2x-1\right)^4=625\)

\(\Leftrightarrow\left[{}\begin{matrix}\left(2x-1\right)^4=5\\\left(2x-1\right)^4=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

Vậy ....

mình cũng hỏi về cái này gấp nha ai biết trả lời câu nào thì trả

\(5^{12}.7-5^{11}.10\)

\(=5^{11}.\left(5.7-10\right)\)

\(=5^{11}.25\)

\(=5^{11}.5^2\)

\(=5^{13}\)

\(2^{20}.15+2^{20}.85\)

\(=2^{20}.5\left(3+17\right)\)

\(=2^{20}.100\)

\(=104857600\)

\(125^3:25^4\)

\(=\left(5^3\right)^3:\left(5^2\right)^4\)

\(=5^9:5^8\)

\(=5\)

\(24^4:3^4-32^{12}:16^{12}\)

\(=\left(24:3\right)^4-\left(32:16\right)^{12}\)

\(=8^4-2^{12}\)

\(=0\)