Jawabanmu

2014-06-01T09:17:12+07:00
F(x) = ax² + bx + c
(1,0)  ----> 0 = a + b + c
(4,0)  ----> 0 = 16a + 4b + c
(0,4)  ----> 4 = 0 + 0 + c
c= 4
substitusi x= 4
0 = a + b + 4 -----a+b = -4
16a + 4b + 4 = 0 -----> 16a + 4b = -4
4(4a + b) = -4
4a + b = -1
eliminasi
4a + b = -1
a + b = -4

3a = 3
a =1
a+b = -4
1 + b = -4
b = -5
y = x² -5x + 4
f(7) = 7² -5(7) + 4
= 18