Diketahui fungsi f didefinisikan dengan rumus f ( x ) = ax +b. Jika f (5 ) = -8 dan f (-2) = 13, nilai dari f ( 3 ) adalah… A. 14 B. 2 C. -2 D. -14

Jawaban:

C.-2

Penjelasan dengan langkah-langkah:

f(x) = ax + b

f(5) = a×5 + b = -8

f(5) = 5a + b = -8(i)

f(-2) = -2a + b = 13(ii)

(Eliminasi)

5a + b = -8

-2a + b= 13

—————–(-)

7a = -21

a = -3

5×(-3) + b = -8

-15 + b = -8

b = 7

f(3) = 3×(-3) + 7

= -9 + 7 = -2(C)

Jawaban:

f(5) = 5a + b = -8

f(-2) = -2a + b = 13

__________-

7a = -21

a = – 3

-2a + b = 13

-2(-3) + b = 13

6 + b = 13

b = 7

f(3) = -3(3) + 7 = -9 + 7 = -2 (C)