Diketahui f(x)=x² +2x+5 dan (f+g)(x)= 2x²−x+3. Tentukan: (f+g)(2) dan (f−g)(2)
Jawabannya adalah (f+g)(2) = 9 dan (f−g)(2)= 4
Konsep :
(f+g)(x) = f(x) + g(x)
(f-g)(x) = f(x) – g(x)
Jawab :
(f+g)(x) = 2x²−x+3
f(x) + g(x) = 2x²−x+3
x² +2x+5 + g(x) = 2x²−x+3
g(x) = 2x²−x+3-x² -2x-5
g(x) = x² – 3x – 2
(f-g)(x) = x² +2x+5 – (2x²−x+3)
= x² +2x+5 – 2x² + x – 3
= -x² + 3x + 2
(f-g)(2) = -2² + 3(2) + 2
= -4 + 6 + 2
= -4 + 8
= 4
(f+g)(2)= 2(2)²−2+3
= 8 – 2 + 3
= 9
Jadi (f+g)(2) = 9 dan (f−g)(2)= 4