Question

Fungsi f(x) = mx + n. Jika f(1) = -2 dan f(5) = 14, maka nilai f(-3) adalah...
a.-12
b. -6
c. 18
d. -18

Answer 1

F(1) = m(1) + n
-2 = m + n......... persamaan 1

f(5) = m(5) + n
14 = 5m + n...... persamaan 2

eliminasi :
m + n = -2
5m + n = 14
dikurangi
-4m = -16
   m = -16 : -4
   m = 4.

substitusi :
m + n = -2
4 + n = -2
     n = -2 -4
     n = -6

jadi, nilai f(-3) = 4 . (-3) + (-6)
             f(-3) = - 12 - 6
             f(-3) = -18

Answer 2

Cari nilai m :
( 14 + 2 ) : ( 5 - 1 ) = 4

Cari nilai n :
-2 = m + n
-2 = 4 + n
 n = -6

Maka, nilai f(-3) :
f(-3) = 4(-3) + (-6)
        = -12 - 6
        = -18