Answer:
Our two intersection points are:
![\displaystyle (3, -2) \text{ and } \left(-\frac{53}{25}, \frac{46}{25}\right)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%283%2C%20-2%29%20%5Ctext%7B%20and%20%7D%20%5Cleft%28-%5Cfrac%7B53%7D%7B25%7D%2C%20%5Cfrac%7B46%7D%7B25%7D%5Cright%29)
Step-by-step explanation:
We want to find where the two graphs given by the equations:
![\displaystyle (x+1)^2+(y+2)^2 = 16\text{ and } 3x+4y=1](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%28x%2B1%29%5E2%2B%28y%2B2%29%5E2%20%3D%2016%5Ctext%7B%20and%20%7D%203x%2B4y%3D1)
Intersect.
When they intersect, their <em>x-</em> and <em>y-</em>values are equivalent. So, we can solve one equation for <em>y</em> and substitute it into the other and solve for <em>x</em>.
Since the linear equation is easier to solve, solve it for <em>y: </em>
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Substitute this into the first equation:
![\displaystyle (x+1)^2 + \left(\left(-\frac{3}{4}x + \frac{1}{4}\right) +2\right)^2 = 16](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%28x%2B1%29%5E2%20%2B%20%5Cleft%28%5Cleft%28-%5Cfrac%7B3%7D%7B4%7Dx%20%2B%20%5Cfrac%7B1%7D%7B4%7D%5Cright%29%20%2B2%5Cright%29%5E2%20%3D%2016)
Simplify:
![\displaystyle (x+1)^2 + \left(-\frac{3}{4} x + \frac{9}{4}\right)^2 = 16](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%28x%2B1%29%5E2%20%2B%20%5Cleft%28-%5Cfrac%7B3%7D%7B4%7D%20x%20%20%2B%20%5Cfrac%7B9%7D%7B4%7D%5Cright%29%5E2%20%3D%2016)
Square. We can use the perfect square trinomial pattern:
![\displaystyle \underbrace{(x^2 + 2x+1)}_{(a+b)^2=a^2+2ab+b^2} + \underbrace{\left(\frac{9}{16}x^2-\frac{27}{8}x+\frac{81}{16}\right)}_{(a+b)^2=a^2+2ab+b^2} = 16](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cunderbrace%7B%28x%5E2%20%2B%202x%2B1%29%7D_%7B%28a%2Bb%29%5E2%3Da%5E2%2B2ab%2Bb%5E2%7D%20%2B%20%5Cunderbrace%7B%5Cleft%28%5Cfrac%7B9%7D%7B16%7Dx%5E2-%5Cfrac%7B27%7D%7B8%7Dx%2B%5Cfrac%7B81%7D%7B16%7D%5Cright%29%7D_%7B%28a%2Bb%29%5E2%3Da%5E2%2B2ab%2Bb%5E2%7D%20%3D%2016)
Multiply both sides by 16:
![(16x^2+32x+16)+(9x^2-54x+81) = 256](https://tex.z-dn.net/?f=%2816x%5E2%2B32x%2B16%29%2B%289x%5E2-54x%2B81%29%20%3D%20256)
Combine like terms:
![25x^2+-22x+97=256](https://tex.z-dn.net/?f=25x%5E2%2B-22x%2B97%3D256)
Isolate the equation:
![\displaystyle 25x^2 - 22x -159=0](https://tex.z-dn.net/?f=%5Cdisplaystyle%2025x%5E2%20-%2022x%20-159%3D0)
We can use the quadratic formula:
![\displaystyle x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20x%20%3D%20%5Cfrac%7B-b%5Cpm%5Csqrt%7Bb%5E2-4ac%7D%7D%7B2a%7D)
In this case, <em>a</em> = 25, <em>b</em> = -22, and <em>c</em> = -159. Substitute:
![\displaystyle x = \frac{-(-22)\pm\sqrt{(-22)^2-4(25)(-159)}}{2(25)}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20x%20%3D%20%5Cfrac%7B-%28-22%29%5Cpm%5Csqrt%7B%28-22%29%5E2-4%2825%29%28-159%29%7D%7D%7B2%2825%29%7D)
Evaluate:
![\displaystyle \begin{aligned} x &= \frac{22\pm\sqrt{16384}}{50} \\ \\ &= \frac{22\pm 128}{50}\\ \\ &=\frac{11\pm 64}{25}\end{aligned}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cbegin%7Baligned%7D%20x%20%26%3D%20%5Cfrac%7B22%5Cpm%5Csqrt%7B16384%7D%7D%7B50%7D%20%5C%5C%20%5C%5C%20%26%3D%20%5Cfrac%7B22%5Cpm%20128%7D%7B50%7D%5C%5C%20%5C%5C%20%26%3D%5Cfrac%7B11%5Cpm%2064%7D%7B25%7D%5Cend%7Baligned%7D)
Hence, our two solutions are:
![\displaystyle x_1 = \frac{11+64}{25} = 3\text{ and } x_2 = \frac{11-64}{25} =-\frac{53}{25}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20x_1%20%3D%20%5Cfrac%7B11%2B64%7D%7B25%7D%20%3D%203%5Ctext%7B%20and%20%7D%20x_2%20%3D%20%5Cfrac%7B11-64%7D%7B25%7D%20%3D-%5Cfrac%7B53%7D%7B25%7D)
We have our two <em>x-</em>coordinates.
To find the <em>y-</em>coordinates, we can simply substitute it into the linear equation and evaluate. Thus:
![\displaystyle y_1 = -\frac{3}{4}(3)+\frac{1}{4} = -2](https://tex.z-dn.net/?f=%5Cdisplaystyle%20y_1%20%3D%20-%5Cfrac%7B3%7D%7B4%7D%283%29%2B%5Cfrac%7B1%7D%7B4%7D%20%3D%20-2)
And:
![\displaystyle y _2 = -\frac{3}{4}\left(-\frac{53}{25}\right) +\frac{1}{4} = \frac{46}{25}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20y%20_2%20%3D%20-%5Cfrac%7B3%7D%7B4%7D%5Cleft%28-%5Cfrac%7B53%7D%7B25%7D%5Cright%29%20%2B%5Cfrac%7B1%7D%7B4%7D%20%3D%20%5Cfrac%7B46%7D%7B25%7D)
Thus, our two intersection points are:
![\displaystyle (3, -2) \text{ and } \left(-\frac{53}{25}, \frac{46}{25}\right)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%283%2C%20-2%29%20%5Ctext%7B%20and%20%7D%20%5Cleft%28-%5Cfrac%7B53%7D%7B25%7D%2C%20%5Cfrac%7B46%7D%7B25%7D%5Cright%29)