Diketahui f(x)=mx+n. Jika f(-1)=1, dan f(3)=9, maka f(1)-f(4)

Kelas 8 Matematika
Bab Fungsi

f(x) = mx + n

f(-1) = -m + n = 1
f(3) = 3m + n = 9
..........----------------- -
-4m = -8
m = -8/-4
m = 2

-m + n = 1
-2 + n = 1
n = 1 + 2
n = 3

f(x) = 2x + 3

f(1) = 2 . 1 + 3
f(1) = 5

f(4) = 2 . 4 + 3
f(4) = 11

f(1) - f(4)
= 5 - 11
= -6

f(x)=mx+n
f(-1)=m(-1)+n=1
f(3)=m(3)+n=9
_____________ -
=4m+0 = -8
m = -8: -4
m = 2

n= 2(3)+n =9
= 6 +n =9-6
=3

= mx+n
= 2x+n
=f(1) = 2x + 3. =f(4) = 2(4) + 3
= 2(1) +3. = 8 + 3
= 2+3. = 11
= 5

= f(1) - f(4)
= 5 - 11
= -6