Jawabanmu

2014-04-09T20:08:43+07:00
-2 =1a+b
19=4a+b
-------------- -
-21 = -3a
a= -7
2014-04-09T20:12:18+07:00
F(x) =ax+b
f(1) = a +b=-2
f(4)= 4a+b=19      _
-----------------------------
       -3a = -21
         a = 7