tolong yg bisa jawab

12. Diket:
sisi = (x-1)
keliling = (3x+5)

Dijawab :
K=4×S(sisi)
(3x+5)= 4×(x-1)
3x+5 =4x-4
3x-4x= -4-5
-x= -9
x= 9
Sisi = (x-1)
=(9-1)
=8 cm
luas persegi
L=S×S
= 8×8
= 64cm

14. Diket
f(x) =ax+b
f(4)=3
f(-1)= -7
f(-5)=?

Dijawab
f(4)= ax+b
3= a(4)+b
3=4a+b
f(-1)= a(-1)+b
-7= -a+b

3=4a+b
-7=-a+b (dikurangi)
10=5a
2=a

f(4)= ax+b
3= 2(4)+b
3=8+b
-5=b
f(x)=ax+b
f(x) =2x-5

f(-5)= 2x-5
=2(-5)-5
=-10-5
=-15 (D)