[數學]precaluclas問題

Q21.
when x = w/2, y = A
so A^2 - (w/2)^2 = 38
now A = 7
so 7^2 - (w/2)^2 = 38
(w/2)^2 = 49 - 38 = 11
w = 2 sqrt 11.



2009-06-03 07:28:37 補充：
Q4. It should be a hyperbola. It cannot be a circle or ellipse because any points on x-axis certainly cannot meet the requirement. It must be symmetrical about the x-axis, so cannot be a parabola.

2009-06-03 07:39:11 補充：
Q3.
Equation of ellipse is x^2/a^2 + y^2/b^2 = 1. When x = 0, b = y. When y = 0,
a = x. For this question, when x = 0, y = 870 + 918 = 1788 = b. When y = 0, x = 870 + 561 = 1431 = a. So the equation is (x/1431)^2 + (y/1788)^2 = 1.