a) 100.10.2.5

= 10².10.10

= 10²⁺¹⁺¹

= 10⁴

b) 16.4.4.2.2.8

= 2⁴.2².2².2².2³

= 2⁴⁺²⁺²⁺²⁺³

= 2¹³

a)
\(100.10.2.5\\ =10^2.10.\left(2.5\right)\\ =10^2.10.10\\ =10^{2+1+1}\\ =10^4\)

b)
\(16.4.4.2.2.8\\ =2^4.2^2.2^2.2.2.2^3\\ =2^{4+2+2+1+1+3}\\ =2^{13}\\ ^{ }\\ \\ \\ \\ \)

\(100-x:15=10,5\\ x:15=100-10,5\\ x:15=89,5\\ x=15\times89,5\\ x=1342,5\)

Vậy: ... 

100 - x : 15 = 10,5

x : 15 = 100 - 10,5

x : 15 = 89,5

x = 89,5 × 15

x = 1342,5

                                     ~~~ the end~~~

\(\left(\dfrac{3}{4}\times x\right):\dfrac{1}{2}=\dfrac{4}{5}\\ \dfrac{3}{4}\times x=\dfrac{4}{5}\times\dfrac{1}{2}\\ \dfrac{3}{4}\times x=\dfrac{4\times1}{5\times2}\\ \dfrac{3}{4}\times x=\dfrac{2}{5}\\ x=\dfrac{2}{5}:\dfrac{3}{4}\\ x=\dfrac{2}{5}\times\dfrac{4}{3}\\ x=\dfrac{2\times4}{5\times3}\\ x=\dfrac{8}{15}\)

Vậy: ...

\(15\times8-\left(17-30+83\right)-144:6\\ =15\times8-\left[\left(17+83\right)-30\right]-24\\ =120-\left(100-30\right)-24\\ =120-70-24\\ =50-24\\ =26\)

\(12+\left(x\times3+5\right):5=16\\ \left(x\times3+5\right):5=16-12\\ \left(x\times3+5\right):5=4\\ x\times3+5=4\times5\\ x\times3+5=20\\ x\times3=20-5\\ x\times3=15\\ x=15:3\\ x=5\)

Vậy: .. 

\(\left(\dfrac{-4}{5}+\dfrac{-3}{2}:x\right)\cdot\dfrac{1}{3}-\dfrac{1}{2}=\dfrac{1}{2}\\ \left(\dfrac{-4}{5}+\dfrac{-3}{2}:x\right)\cdot\dfrac{1}{3}=\dfrac{1}{2}+\dfrac{1}{2}\\ \left(\dfrac{-4}{5}+\dfrac{-3}{2}\right):x\cdot\dfrac{1}{3}=1\\ \dfrac{-4}{5}+\dfrac{-3}{2}:x=1:\dfrac{1}{3}\\ -\dfrac{4}{5}+\dfrac{-3}{2}x=3\\ \dfrac{3}{2}x=\dfrac{-4}{5}-3\\ \dfrac{3}{2}x=-\dfrac{19}{5}\\ x=\dfrac{-19}{5}:\dfrac{3}{2}\\x =-\dfrac{38}{15}\)

a: Oz là phân giác của góc xOy

=>\(\widehat{xOz}=\widehat{yOz}=\dfrac{\widehat{xOy}}{2}=\dfrac{80^0}{2}=40^0\)

gọi oz là tia PG của oy 😤 đề sai r

\(4^2+5=y^2+y\\ =>16+5=y^2+y\\ =>21=y^2+y\\ =>y^2+y-21=0\\ =>\left(y^2+\dfrac{1}{2}y+\dfrac{1}{2}y+\dfrac{1}{4}\right)-\dfrac{85}{4}=0\\ =>\left[y\left(y+\dfrac{1}{2}\right)+\dfrac{1}{2}\left(y+\dfrac{1}{2}\right)\right]=\dfrac{85}{4}\\ =>\left(y+\dfrac{1}{2}\right)\left(y+\dfrac{1}{2}\right)=\dfrac{85}{4}\\ =>\left(y+\dfrac{1}{2}\right)^2=\left(\dfrac{\sqrt{85}}{2}\right)^2\\ TH1:y+\dfrac{1}{2}=\dfrac{\sqrt{85}}{2}\\ =>y=\dfrac{\sqrt{85}-1}{2}\\ TH2:y+\dfrac{1}{2}=-\dfrac{\sqrt{85}}{2}\\ =>y=\dfrac{-\sqrt{85}-1}{2}\)

Đề sai rồi á bạn, mình nghĩ là phải chia hết cho 120 hoặc 100 chứ biểu thức đó k chia hết cho 105 đâu