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Given the system of equations:
To solve it by substitution, follow the steps below.
Step 1: Solve one linear equation for x in terms of y.
Let's choose the second equation. To solve it for x, add 3y to each side of the equations.
Step 2: Substitute the expression found for x in the first equation.
Step 3: Isolate y in the equation found in step 2.
To do it, first, add 48 to both sides.
Then, divide both sides by 15.
Step 4: Substitute y by 5 in the relation found in step 1 to find x.
Answer:
x = -9
y = 5
or (-9, 5)
Also, you can graph the lines by choosing two points from each equation, according to the picture below.
Answer:
y = -1/8(x -1)² +4
Step-by-step explanation:
The equation of a parabola can be written from focus and directrix using the form ...
y = 1/(4p)(x -h)² +k
where p is the distance from vertex to focus, and (h, k) is the vertex.
The vertex-focus distance is half the distance from the directrix to the focus. Here, that is ...
p = (2 -6)/2 = -4/2 = -2
The vertex is halfway between the focus and directrix on the same vertical line, so has coordinates ...
(h, k) = ((1, 2) +(1, 6))/2 = (1, 4)
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Using these values of p and (h, k), we find the equation of the parabola to be ...
y = 1/(4(-2))(x -1)² +4
y = -1/8(x -1)² +4
_____
<em>Additional comment</em>
You can check the graph by considering the definition of a parabola: each point on the curve is equidistant from the focus and the directrix. This is easily verified for points on the horizontal and vertical lines through the focus. For example, point (5, 2) is 4 units from the focus, and 4 units from the directrix.
