109 c
7.
(x-4)^2/25+(y+2)^2/144=1 求頂點，正焦弦長
中心點O=(4,-2)
長軸a=12 on y axis
短軸b=5
頂點
O+(0,12)
O-(0,12)
O+(5,0)
O-(5,0)
焦距c=sqrt(a^2-b^2)
焦點O+(0,c)
焦點O+(0,-c)
正焦弦長 d=2b^2/a
10.
x+2y-6>=0
x+y-10<=0
2<=x<=9
求解的面積
x+2y-6=0
x|2 |9
-------------
y|2 |-3/2
x+y-10=0
x|2 |9
-------------
y|8 |1
11.
f(x)=2cos(3x)-1
a=f(x)與x軸的交點數
b=f(x) max
solve ab=?
-1<=cos3x<=1
-2-1<=cos3x-1<=2-1
-3<=cos3x-1<=1
b=f(x) max=1
cosx period= 2pi
cos3x period=2pi/3
13.
f(x)=x^3-3x^2-24x+32 on [-3,3]
m=f(x) max, n=f(x) min, solve m-n=?
