We know that
the equation of the parabola is of the form
y=ax²+bx+c
in this problem
y=1/4x²−x+3
where
a=1/4
b=-1
c=3
the coordinates of the focus are
(-b/2a,(1-D)/4a)
where D is the discriminant b²-4ac
D=(-1)²-4*(1/4)*3-----> D=1-3---> D=-2
therefore
x coordinate of the focus
-b/2a----> 1/[2*(-1/4)]----> 2
y coordinate of the focus
(1-D)/4a------> (1+2)/(4/4)---> 3
the coordinates of the focus are (2,3)
The answer is D
Let me know if it’s right!
Take the original price, multiply it by 20% (you have to move the decimal place two to the left, so it becomes .2), then subtract the answer from the original price.
39.99*.2= $7.998
39.99-7.998= $31.99
If you wanted to, you could also round the $7.998 to $8.00. Your answer would be the same.
