26. 已知 x 和 y 滿足x2+y2-4x-6y-12=0,則|3x-4y|的最大值為何?
(A)6
(B)19
(C)31
(D)50
【用戶】mark123
【年級】幼兒園下
【評論內容】x2+y2-4x-6y-12=0(x-2)2 +(y-3)2 =52x=2+5cos(m)y=3+5sin(m)3x-4y=[15cos(m)-20sin(m)] -6而(-25)<= [15cos(m)-20sin(m)] <=25so,絕對值(3x-4y)的最大值 =絕對值(-25-6) =31
【用戶】mark123
【年級】幼兒園下
【評論內容】x2+y2-4x-6y-12=0(x-2)2 +(y-3)2 =52x=2+5cos(m)y=3+5sin(m)3x-4y=[15cos(m)-20sin(m)] -6而(-25)<= [15cos(m)-20sin(m)] <=25so,絕對值(3x-4y)的最大值 =絕對值(-25-6) =31