55.
perhaps the point of tangency is (a,4a-a^2)
as the tangent line pass through (2,5)
we know
the slope of the tangent line is
K = (4a-a^2-5)/(a-2)
and the derivative of f(x) is
4-2x
we also have
K = 4-2a
so
(4a-a^2-5)/(a-2) = 4-2a
a=1 or 3
K=2 or -2
then .....
67.y'=1+cosx
when x = pi
y'=0作者: super6358 時間: 2013-11-2 04:04 PM
