math1-http://postimg.org/image/5i4uwnaoz/?

1.
f(x) = (x + 5)/21
f(1) = (1 + 6)/21 = 7/21
f(2) = (2 + 6)/21 = 8/21
f(3) = (3 + 6)/21 = 9/21
f(1) + f(2) + f(3) = (7 + 8 + 9)/21 = 21/21 = 1
Yes

2a)
P(1)+P(2)+P(3)+P(4)+P(5)
=0.5+0.2+0.15+0.1+0.05
=1
Yes

2b)
P(1)+P(2)+P(3)+P(4)+P(5)
=0.1+0.1+0.15+0.2+0.55
=1.1>1
No

2c)
c)
P(3)=-0.15<0
No