Suatu fungsi di nyatakan sebagai f(x) =ax+b, jika f(5) =25 dan f(4) =-11 nilai dari f(2) -f(5) adalah

f (x) = ax + b
f (5) = 25
f (4) = -11
f (2) - f (5) = ...?
Jawab :
f (x) = ax + b
f (5) = 5a + b = 25
f (4) = 4a + b = -11

5a + b = 25 ··· (1)
4a + b = -11 ··· (2)
_________ --
a = 36

5a + b = 25 ··· (1)
5.36 + b = 25
180 + b = 25
b = 25 - 180
b = -155


f (2) = 2a + b
f (2) = 2.36 + ( -155 )
f (2) = 72 - 155
f (2) = -83

f (5) = 5a + b
f (5) = 5.36 + ( -155 )
f (5) = 180 - 155
f (5) = 25

Maka,
f (2) - f (5)
= -83 - 25
= -108