1. KELOMPOK b
KETUA :
NI LUH GEDE WITASARI (02)
HP : 081999112677
ANGGOTA KELOMPOK :
1.I PUTU PRAMANA PUTRA (18)
2.NI WAYAN NITA ANGGRENI (21)
3.NI KADE INDAH PADMA YANI (31)
4.I GUSTI AYU PUTU DIAN PUTRI LESTARI (32)
TUGAS I :
1. Pembahasan :
Luas = p x l
1000 = (60-x)(30-x)
1000 = 1800 – 60x – 30x + x2
1000 = 1800 – 90x + x2
0
= 1800 – 1000 – 90x + x2
0
= 800 – 90x + x2
0
= x2 – 90x + 800
Jadi persamaan kuadrat dari soal diatas adalah x2 – 90x + 800

2. 2. Pembahasan :
50cm
15 x
x
x
x
40cm
200cm
x
x
x
Volume = p x l x t
x
p = 50 – 2x
l = 40 – 2x
Luas =p x l
200
=(50 – 2x)(40 – 2x)
200
=2000 – 100x – 80x + 4x2
200
=2000 – 180x + 4x2
0
=2000 – 200 – 180x + 4x2
0
=1800 – 180x + 4x2
0
=4x2 – 180x + 1800
0
=x2 – 45x + 450
0
=x2 – 30x – 15x + 450
0
=x(x – 30) – 15(x – 30)
0
=(x – 15)(x – 30)
(x – 15) = 0 atau (x – 30) = 0
:4

3. x – 15 = 0
x
atau
= 15
x – 30 = 0
x
= 30
p = 50 – 2x
l = 40 – 2x
p = 50 – 2.15
l = 40 – 2.15
p = 50 – 30
l = 40 - 30
p = 20
l = 10
atau
p = 50 – 2x
l = 40 – 2x
p =50 – 2.30
l = 40 – 2.30
p = 50 – 60
l = 40 - 60
p = -10
l = -20
Jadi nilai x adalah 15cm,
uji :
luas alas = p x l
luas alas = p x l
= 20 x 10
atau
= 200 cm2
Jadi tinggi balok =p – 20 : 2
= (-10) x (-20)
= 200 cm2
atau
t = l – 10 : 2
=50 – 20 : 2
t = 40 – 10 : 2
=30 : 2
t = 30 : 2
=15
t = 15

4. Sehingga volume balok = p x l x t
= 20 x 30 x15
= 60 x 15
= 3000cm3
3.Pembahasan :
Volume mula – mula kerucut :
V=
r2t
Volume karena penambahan jari – jari sebesar 24 cm :
V=
r2t
V=
(r + 24)3
V = (r + 24)
V1 = (r + 24)
Volume karena penambahan tinggi sebesar 24 cm :
V=
r2t
V=
r2(3 + 24)
V=
r227
2
V= r
V2= 9 r2
V1
( r + 24)2
=
=
V2
9 r2

5. r2 + 48r + 576
0
0
0
0
0
0
=
=
=
=
=
=
=
9r2
9r2 – r2 – 48r – 576
8r2 – 48r – 576
r2 – 6r – 72
r2 + 6r – 12r + 72
r(r + 6) – 12(r + 6)
(r – 12)(r + 6)
:8
(r – 12) = 0 atau (r + 6) = 0
Jadi :
(r – 12) = 0
r – 12 = 0
r
= 12
atau
Sehingga jari – jari kerucut semula 12 cm
4. Pembahasan :
P1 = x – 1 jam
P2 = x jam
P1 + P2 = 1,2 jam
Penyelesaian : 1 : (
1:(
1:
1x
) = 1,2
+
) = 1,2
= 1,2
= 1,2
x2 – x = 2x – 1 . 1,2
x2 – x = 2,4x – 1,2
x2 = 2,4 x + x – 1,2
x2 = 3,4x – 1,2
(r + 6) = 0
r+6 =0
r
= -6

6. 0 = -x2 + 3,4 – 1,2
x2 – 3,4 + 1,2 = 0
10x2 – 34x + 12 = 0
5x (2x – 6) + 2(2x – 6) = 0
(5x + 2) (2x – 6) = 0
(5x + 2) = 0 atau (2x – 6) = 0
5x = -2 atau
2x = 6
x1 =
x2 =
x2 = 3
Jadi waktu yang dibutuhkan printer jenis kedua adalah 3 jam