Answer
a) 55.6 million
b) 94.4 million
c) 2015-2016
Work Step by Step
a)
$2010-2009=1$
$c(x)=-.4x^2+21x+35$
$c(1)=-.4*1^2+21*1+35$
$c(1)=-.4+21+35$
$c(1)=55.6$
b)
$2012-2009=3$
$c(x)=-.4x^2+21x+35$
$c(3)=-.4*3^2+21*3+35$
$c(3)=-.4*9+63+35$
$c(3)=-3.6+98$
$c(3)=94.4$
c)
$c(x)=-.4x^2+21x+35$
$150=-.4x^2+21x+35$
$0=-.4x^2+21x-115$
$x=(-b±\sqrt {b^2-4ac})/2a$
$x=(-21±\sqrt {21^2-4*(-.4)*(-115)})/2*(-.4)$
$x=(-21±\sqrt {441-1.6*115})/-.8$
$x=(-21±\sqrt {441-184})/-.8$
$x=(-21±\sqrt {257})/-.8$
$x=(-21±16.03)/-.8$
$x=(-21±16.03)/-.8$
$x=(-21+16.03)/-.8$
$x=-5.03/-.8$
$x=6.2875$
$x=(-21±16.03)/-.8$
$x=(-21-16.03)/-.8$
$x=-37.03/-.8$
$x=46.2875$
We want the lower value for $x$.
$x=6.2$
$2009+6.2=2015.2$
