Question

Sebuah fungsi ditentukan oleh rumus f(x) =px+q dengan p dan q bilangan bulat . Jika di tentukan f(-3) = -19 dan f(4)=9 ,hitunglah nilai dari f(-5) + f(12)
Jawab : ............

Answer 1

F(-3) = -19
-3p + q = -19

f(4) = 9
4p + q = 9

4p + q = 9
-3p + q = -19 -
--------------------
7p = 28
p = 28 : 7
p = 4

4p + q = 9
4 × 4 + q = 9
16 + q = 9
q = 9 - 16
q = -7

f(x) = 4x - 7

f(-5) + f(12)
= (4 × (-5) - 7) + (4 × 12 - 7)
= (-20 - 7) + (48 - 7)
= -27 + 41
= 14

Answer 2

F(x) = px + q
f(-3) = - 19 ---> -3p + q = -19 .....(persamaan 1)
f(4)  = 9 --> 4p + q = 9 ......(persamaan  2)
..
pers1 dan pers 2 di eliminasikan

-3p + q = -19
4p + q = 9
kurangkan --> -7p = - 28
p = 28 /7 = 4

-3p + q = -19
q = -19 + 3p
q = -19+ 3(4) 
q = -19 +12 = -7

f(x) = px + q  --> f(x)= 4x - 7
f(-5) + f(12)= 4(-5) - 7 + 4(12) - 7
f(-5) + f(12)  = -20 -7 + 48 - 7 = 14