Diketahui f(2x+6) = 5x – 4 nilai f(4) adalah…

Cari f(x) nya dengan mengubah 2x+6

misal.
2x+6= y
2x = y – 6
x = y – 6 / 2
= x – 6/ 2

jadi
f(x) = 5(x – 6/2) – 4
f(4) = 5(4-6/2) – 4
= -5-4 = -9

F (2x + 6) = 5x – 4

misalkan
2x + 6 = a
x = (a – 6) : 2

f (2x + 6) = 5x – 4
f (a) = [5 (a – 6) : 2 ] – 4
f (a) = [(5a – 30) : 2 ] – 8/2
f (a) = (5a – 38) : 2

f (4) = ?

f (x) = (5x – 38) : 2
f (4) = (5 . 4 – 38) : 2
= (20 – 38) : 2
= -18 : 2
= -9

semoga membantu:)