Jika diketahui f(x) + f(x+3) = 2x + 5 f(8)+f(2)=13, maka f(5)=? Pakai caranya plz

jika f(x) + f(x+3) = 2x + 5

misal x = 2, maka x + 3 = 5

maka f(2) + f(5) = 2*2 + 5

f(2) + f(5) = 9 ... (i)


lalu
misal x = 5, maka x + 3 = 8

maka f(5) + f(8) = 2*5 + 5
f(5) + f(8) = 15 ... (ii)

eliminasi (i) dan (ii) didapat

f(2) + f(5) = 9
f(5) + f(8) = 15
===========( + )
f(2) + 2*f(5) + f(8) = 9+15
13 + 2f(5) = 24
2f(5) = 11
f(5) = 11/2 = 6,5 ✔️

semoga jelas dan membantu