tolong jawab pakai cara

a.
f(x) = sx + t

f(3) = 13
3s + t = 13

f(-1) = 1
-s + t = 1

eliminasi
3s + t = 13
-s + t = 1
---------------- -
4s = 12
s = 12 / 4
s = 3

Substitusi
-s + t = 1
-3 + t = 1
t = 1 + 3
t = 4

b.
f(x) = sx + t
s = 3
t = 4

bentuk fungsinya f(x) = 3x + 4

c.
f(x) = 3x + 4
f(5) = 3(5) + 4
f(5) = 15 + 4
f(5) = 19