All you do is subtract the two numbers
Part 1: The general form for this matches y^2 = -4cx, which implies that this opens to the left. (Imagine assigning any value of y, whether positive or negative, which would result in a positive left-hand value. Then to match this sign, the value of x must be negative so that the right-hand side becomes positive as well.)
Part 2: The distance from the vertex to the directrix is given by c. This equation has its vertex at the origin (0, 0). If it opens to the left, the directrix is a vertical line to the right of the origin. This equation is y^2 = -4(1/2)x, so c = 1/2, and the directrix has the equation x = 1/2.
Part 3: The focus is inside the parabola, but it is the same distance from the vertex as the directrix. This distance is 1/2 units, and it will be to the left of the vertex. So the focus is at (-1/2, 0).
Step-by-step explanation:
N=number of nickels
d=number of dimes
q=number of quarters
example
if n:d=3:8
lets say n=3 and d=8
3*8=8*3
so
8n=3d
slightly confusing but go with it, it migh make sense or it might not
n:d=3:8
8n=3d
d:q=4:5
5d=4q
solve for one of them
solve for nickels in first and quarters in second
8n=3d, n=(3/8)d
5d=4q, (4/5)d=q
5n+10d+25q=690
divide by 5 to make it easeir
n+2d+4q=138
sub (3/8)d for n
sub (4/5)d for q
(3/8)d+2d+5(5/4)d=138
(3/8)d+2d+25/4d=138
3/8+2+25/4=
3/8+16/2+50/8=
69/8
(69/8)d=138
times both sides by 8
69d=1104
divide both sides by 69
d=16
16 dimes
sub back
(5/4)d=q
(5/4)16=q
80/4=q
20=q
(3/8)d=n
(3/8)16=n
48/8=n
6=n
6 nickles
16 dimes
20 quarters
yah
