fungsi f F(x) = ax+b jika f(4)= 31 dan f(2) = -32 maka nilai a + b adalah

f(x) = ax+b
f(4)= 31 maka 4a + b = 31
f(2) = -32 maka 2a + b = -32

4a + b = 31
2a + b = -32
------------------ (dikurangkan)
(4a - 2a) + (b - b) = [31 - (-32)]
2a = 63
a = 63/2 = 31,5

4a + b = 31
b = 31 - 4a = 31 - (4x31,5) = -95

a + b = 31,5 + (-95) = -63,5

Matpel : Matematika
Kelas : 8 SMP
Bab : Relasi dan Fungsi

Jawaban :
[tex]f(x) = ax + b \\ f(4) = 31 \\ f(2) = - 32 \\ f(4) = a(4) + b \\ 31 = 4a + b \\ f(2) = a(2) + b \\ - 32 = 2a + b \\ 4a + b = 31 \: pers \: 1\\ 2a + b = - 32 \: pers \: 2\\ pers \: 1 - pers \: 2 = 2a = 63 \\ a = 63/2 \\ \\ subs \: ke \: pers \: 1 \\ 4( 63/2) + b \\ 126 + b \\ b = -126 \\ \\ ditanya \: a + b \\ 63/2 -126 \\ = -189/2[/tex]