The first one includes both
Answer:
![\large\boxed{x\dfrac{17}{7}}\\\downarrow\\\boxed{x\in\left(-\infty,\ -\dfrac{117}{7}\right)\ \cup\ \left(\dfrac{17}{7};\ \infty\right)}](https://tex.z-dn.net/?f=%5Clarge%5Cboxed%7Bx%3C-%5Cdfrac%7B117%7D%7B7%7D%5C%20or%5C%20x%3E%5Cdfrac%7B17%7D%7B7%7D%7D%5C%5C%5Cdownarrow%5C%5C%5Cboxed%7Bx%5Cin%5Cleft%28-%5Cinfty%2C%5C%20-%5Cdfrac%7B117%7D%7B7%7D%5Cright%29%5C%20%5Ccup%5C%20%5Cleft%28%5Cdfrac%7B17%7D%7B7%7D%3B%5C%20%5Cinfty%5Cright%29%7D)
Step-by-step explanation:
![|0.7x+5|>6.7\iff0.7x+5>6.7\ or\ 0.7x+56.7\qquad\text{subtract 5 from both sides}\\0.7x>1.7\qquad\text{divide both sides by 0.7}\\x>\dfrac{1.7}{0.7}\to x>\dfrac{17}{7}\\\\(2)\\0.7x+5](https://tex.z-dn.net/?f=%7C0.7x%2B5%7C%3E6.7%5Ciff0.7x%2B5%3E6.7%5C%20or%5C%200.7x%2B5%3C-6.7%5C%5C%5C%5C%281%29%5C%5C0.7x%2B5%3E6.7%5Cqquad%5Ctext%7Bsubtract%205%20from%20both%20sides%7D%5C%5C0.7x%3E1.7%5Cqquad%5Ctext%7Bdivide%20both%20sides%20by%200.7%7D%5C%5Cx%3E%5Cdfrac%7B1.7%7D%7B0.7%7D%5Cto%20x%3E%5Cdfrac%7B17%7D%7B7%7D%5C%5C%5C%5C%282%29%5C%5C0.7x%2B5%3C-6.7%5Cqquad%5Ctext%7Bsubtract%205%20from%20both%20sides%7D%5C%5C0.7x%3C-11.7%5Cqquad%5Ctext%7Bdivide%20both%20sides%20by%200.7%7D%5C%5Cx%3C%5Cdfrac%7B-11.7%7D%7B0.7%7D%5Cto%20x%3C-%5Cdfrac%7B117%7D%7B7%7D%5C%5C%5C%5C%5Ctext%7BFrom%20%281%29%20and%20%282%29%20we%20have%7D%5C%5Cx%3C-%5Cdfrac%7B117%7D%7B7%7D%5C%20or%5C%20x%3E%5Cdfrac%7B17%7D%7B7%7D%5Cto%20x%5Cin%5Cleft%28-%5Cinfty%2C%5C%20-%5Cdfrac%7B117%7D%7B7%7D%5Cright%29%5C%20%5Ccup%5C%20%5Cleft%28%5Cdfrac%7B17%7D%7B7%7D%3B%5C%20%5Cinfty%5Cright%29)
Answer:
![y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )](https://tex.z-dn.net/?f=y%3De%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2B%5Cfrac%7B1%7D%7B%5Csqrt%7B3%7D%7D%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%20%5Cright%20%29)
Step-by-step explanation:
A second order linear , homogeneous ordinary differential equation has form
.
Given: ![y''+y'+y=0](https://tex.z-dn.net/?f=y%27%27%2By%27%2By%3D0)
Let
be it's solution.
We get,
![\left ( r^2+r+1 \right )e^{rt}=0](https://tex.z-dn.net/?f=%5Cleft%20%28%20r%5E2%2Br%2B1%20%5Cright%20%29e%5E%7Brt%7D%3D0)
Since
, ![r^2+r+1=0](https://tex.z-dn.net/?f=r%5E2%2Br%2B1%3D0)
{ we know that for equation
, roots are of form
}
We get,
![y=\frac{-1\pm \sqrt{1^2-4}}{2}=\frac{-1\pm \sqrt{3}i}{2}](https://tex.z-dn.net/?f=y%3D%5Cfrac%7B-1%5Cpm%20%5Csqrt%7B1%5E2-4%7D%7D%7B2%7D%3D%5Cfrac%7B-1%5Cpm%20%5Csqrt%7B3%7Di%7D%7B2%7D)
For two complex roots
, the general solution is of form ![y=e^{\alpha t}\left ( c_1\cos \beta t+c_2\sin \beta t \right )](https://tex.z-dn.net/?f=y%3De%5E%7B%5Calpha%20t%7D%5Cleft%20%28%20c_1%5Ccos%20%5Cbeta%20t%2Bc_2%5Csin%20%5Cbeta%20t%20%5Cright%20%29)
i.e ![y=e^{\frac{-t}{2}}\left ( c_1\cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )](https://tex.z-dn.net/?f=y%3De%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20c_1%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2Bc_2%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%20%5Cright%20%29)
Applying conditions y(0)=1 on
, ![c_1=1](https://tex.z-dn.net/?f=c_1%3D1)
So, equation becomes ![y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )](https://tex.z-dn.net/?f=y%3De%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2Bc_2%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%20%5Cright%20%29)
On differentiating with respect to t, we get
![y'=\frac{-1}{2}e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )+e^{\frac{-t}{2}}\left ( \frac{-\sqrt{3}}{2} \sin \left ( \frac{\sqrt{3}t}{2} \right )+c_2\frac{\sqrt{3}}{2}\cos\left ( \frac{\sqrt{3}t}{2} \right )\right )](https://tex.z-dn.net/?f=y%27%3D%5Cfrac%7B-1%7D%7B2%7De%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2Bc_2%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%20%5Cright%20%29%2Be%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20%5Cfrac%7B-%5Csqrt%7B3%7D%7D%7B2%7D%20%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2Bc_2%5Cfrac%7B%5Csqrt%7B3%7D%7D%7B2%7D%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%5Cright%20%29)
Applying condition: y'(0)=0, we get ![0=\frac{-1}{2}+\frac{\sqrt{3}}{2}c_2\Rightarrow c_2=\frac{1}{\sqrt{3}}](https://tex.z-dn.net/?f=0%3D%5Cfrac%7B-1%7D%7B2%7D%2B%5Cfrac%7B%5Csqrt%7B3%7D%7D%7B2%7Dc_2%5CRightarrow%20c_2%3D%5Cfrac%7B1%7D%7B%5Csqrt%7B3%7D%7D)
Therefore,
![y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )](https://tex.z-dn.net/?f=y%3De%5E%7B%5Cfrac%7B-t%7D%7B2%7D%7D%5Cleft%20%28%20%5Ccos%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%2B%5Cfrac%7B1%7D%7B%5Csqrt%7B3%7D%7D%5Csin%20%5Cleft%20%28%20%5Cfrac%7B%5Csqrt%7B3%7Dt%7D%7B2%7D%20%5Cright%20%29%20%5Cright%20%29)
Answer:
14
Step-by-step explanation:
7*3=21
2/3 of 21 is 14 so she saved 14 dollars
The x axis of the graph show the distance driven and y axis represnt Gas remains
at 40 miles of distance i.e x =40
Then value of y at x = 40 is 3.5 i.e. y = 3.5