5+2.5+5+3.5+...+5+9.5=
\(P=\dfrac{2.5^{22}-9.5^{20}}{25^{10}}:\dfrac{5\left(3.7^{15}-19.7^{14}\right)}{7^{16}+3.7^{15}}\)
Đặt P= \(\dfrac{2.5^{22}-9.5^{21}}{25^{10}}\) : \(\dfrac{5.\left(3.7^{15}-19.7^{14}\right)}{\left(7^{16}+3.7^{15}\right)}\)
Có : \(\dfrac{2.5^{22}-9.5^{21}}{25^{10}}\)
= \(\dfrac{\left(2.5-9\right).5^{21}}{\left(5^2\right)^{10}}\)= \(\dfrac{\left(10-9\right).5^{21}}{5^{20}}\)=\(\dfrac{5^{21}}{5^{20}}\)= 5 (1)
Có: \(\dfrac{5.\left(3.7^{15}-19.7^{14}\right)}{\left(7^{16}+3.7^{15}\right)}\)
= \(\dfrac{5.\left[7^{14}.\left(3.7-19\right)\right]}{\left[7^{15}.\left(3+7\right)\right]}\)=\(\dfrac{5.7^{14}.2}{7^{15}.10}\)=\(\dfrac{10.7^{14}}{7^{15}.10}\)=\(\dfrac{1}{7}\) (2)
Từ (1) và (2) suy ra:
A= 5:\(\dfrac{1}{7}\)=5.7=35
Vậy A=35 hay \(\dfrac{2.5^{22}-9.5^{21}}{25^{10}}\):\(\dfrac{5.\left(3.7^{15}-19.7^{14}\right)}{\left(7^{16}+3.7^{15}\right)}\)= 35
\(P=\dfrac{2.5^{22}-9.5^{20}}{25^{10}}:\dfrac{5\left(3.7^{15}-19.7^{14}\right)}{7^{16}+3.7^{15}}\)
\(=\dfrac{5^{20}\left(2.5^2-9\right)}{5^{20}}:\dfrac{5.7^{14}\left(3.7-19\right)}{7^{15}\left(7+3\right)}\)
\(=\left(2.5^2-9\right):\dfrac{5\left(3.7-19\right)}{7.10}\)
\(=\dfrac{7.10\left(2.5^2-9\right)}{5\left(3.7-19\right)}\)
\(=\dfrac{7.2\left(2.5^2-9\right)}{3.7-19}\)
\(=\dfrac{14.41}{21-19}\)
\(=\dfrac{14}{2}\cdot41=7.41=287\)
Tìm x,biết
A) (-3)^2x=9^5
B) 9.5^ x-3=6.5^6+3.5^6
C) 5^x+4-3.5^x+3=5^11.2
D) 3^x+2+4.3^x+1=7.3^6
E) 5^x+3=10^5.6^3:4^4.3^3
Tìm x, biết:
\(5^{x-11}-2.5^2=3.5^3\)
5x-11 - 2.52 = 3.53
5x-11 - 2.25 = 3.125
5x-11 - 50 = 375
5x-11 = 375 + 50
5x-11 = 425
.....
=>x thuộc rỗng nhé
5x-11-2.25=3.125
5x-11-50=375
5x-11=375+50
5x-11=425
đề sai rồi vì 5 mũ mấy cũng ko bằng 425 đâu
5^x+4-3.5^x+3=2.5^11
\(\Leftrightarrow5^x\cdot625-3\cdot5^x\cdot125=2\cdot5^{11}\)
\(\Leftrightarrow5^x\cdot250=2\cdot5^{11}\)
\(\Leftrightarrow5^x=5^8\)
hay x=8
5^(x+4) -3.5^(x+3)=2.5^1
Ta có:\(5^{x+4}-3\cdot5^{x+3}=2\cdot5\)
\(5^x\cdot5^4-3\cdot5^x\cdot5^3=10\)
\(5^x\left(5^4-3\cdot5^3\right)=10\)
\(5^x\cdot250=10\)
\(5^x=10:250\)
\(5^x=\frac{1}{25}\)
\(5^x=5^{-2}\)
\(\Rightarrow x=-2\)
\(5^{x+4}-3.5^{x+3}=2.5\)
\(\Rightarrow5^{x+3}.5-3.5^{x+3}=2.5\)
\(\Rightarrow5^{x+3}.\left(5-3\right)=2.5\)
\(\Rightarrow5^{x+3}.2=2.5\)
\(\Rightarrow5^{x+3}=5\)
\(\Rightarrow x+3=1\)
\(\Rightarrow x=-2\)
Vậy \(x=-2\)
5^x+4-3.5^x-3=2.5^11
5^x+4-3.5^x-3=2.5^11
5^x+4-3.5^x-3+2.5^11
5^x+4-3.5^x-3=2.5^11
ai tick cho mình đi
mình sẽ cảm ơn!!!!!!
thanks