1.5.3 Fungsi, SPM Praktis (Soalan Pendek)


1.5.3 Fungsi, SPM Praktis (Soalan Pendek)
Soalan 8:
Cari fungsi songsangan f ( x ) = 3 x + 2 5 x + 3

Penyelesaian:
f(x)= 3x+2 5x+3 katakan y= 3x+2 5x+3 y( 5x+3 )=3x+2 5xy+3y=3x+2 5xy3x=23y x( 5y3 )=23y x= 23y 5y3 f 1 ( x )= 23x 5x3 tukar y kepada x untuk cari  f 1 ( x ) 


Soalan 9:
(a) Jika f : xx – 2, cari f -1 (5), 
(b) Jika f : x x + 9 x 5 , x 5 , cari f 1 ( 3 ) .  

Penyelesaian:
(a)
f (x) = x– 2
Katakan y = f -1 (5)
f (y) = 5
y – 2 = 5
y = 7
oleh itu, f -1 (5) = 7

(b)
f(x)= x+9 x5 katakan y= f 1 (3) f(y)=3 y+9 y5 =3 y+9=3y15 2y=24 y=12 f 1 ( 3 )=7

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