1. 1. Selesaikan persamaan kuadrat di bawah dengan cara memfaktorkan
a. x2 + 5x - 50 = 0
b. x2 + 3x = 0
c. x2 - 4 = 0
d. 2x2 + 3x + 1 = 0
e. 3x2 + 5x - 2 = 0
Jawab:
a.
x2 + 5x - 50 = 0
x2 + 10x – 5x – 50 = 0
(x2 + 10x) – (5x – 50) = 0
x(x + 10) – 5(x + 10) = 0
(x – 5) (x + 10) = 0
x = 5 atau x = -10
b. x2 + 3x = 0
x2 + 2x + x = 0
(x2 + 2x) + x = 0
x(x + 3) = 0
x = -3
c. x2 - 4 = 0
x2 + 2x – 2x – 4 = 0
(x2 +2x) – (2x – 4) = 0
x(x + 2) – 2(x + 2) = 0
(x – 2) (x + 2) = 0
x = 2 atau x = -2
d. 2x2 + 3x + 1 = 0
2x2 + 2x + x + 1 = 0
(2x2 + 2x) + (x + 1) = 0
2x(x +1) + (x + 1) = 0
(2x + 1) (x +1) = 0
x = - atau x = -1

2. e. 3x2 + 5x - 2 = 0
3x2 – x + 6x -2 = 0
(3x2 – x) + (6x – 2) = 0
x(3x – x) + 2(3x –1) = 0
(x + 2) (3x – 1) = 0
x = -2 atau x =
2. Selesaikan persamaan kuadrat berikut ini dengan melengkapkan kuadrat sempurna
a. x2 + 5x +4 = 0
b. 2x2 – 14x + 12 = 0
Jawab:
a. x2 + 5x +4 = 0
x2 + 5x +4 – 4 = 0 -4
x2 + 5x + (
)2 = (
)2 – 4
(x + 5)2 = ( 5)2 – 4
2
(x + 5) = ±
-4
2
X =- 5±
2
= -2,5 ±
-4
-4
= -2,5±
= -2,5 ±
= -2,5± 1,5
x = -2,5 + 1,5 = -1, atau
x = -2,5 – 1,5 = -4
b. 2x2 – 14x + 12 = 0
X2 – 7x + 6 = 0
X2 – 7x + 6 – 6 = 0 – 6
X2 – 7x + ( 7)2 = ( .7)2 – 6
(x + 7)2 = ( 7)2 – 6
(x + 7) = ±
X=- 7±
2
-6
2
-6

3. 2
= -3,5 ±
-6
= -3,5±
= -3,5 ±
= -3,5± 2,5
X = -3,5 + 2,5 = -1 atau
X = -3,5 – 2,5 = -6
3. Selesaikan persamaan kuadrat berikut ini dengan rumus abc
a. x2 - 15x + 30 = 0
Jawab:
X1,2
b. x2+ 8x - 20 = 0
Jawab:
X1,2
X1
= =2
X2 =
=
= -10

4. c. x 2 + 3x = 0
Jawab:
X1,2
X1
X2 =
=
= -3
4. Tentukan p agar persamaan kuadrat (p+3)x2 + 3x - 4 = 0 mempunyai dua akar sama.
Jawab:
(p+3)x2 + 3x - 4 = 0
D = b2 – 4ac
= 32 – 4(p+3). – 4
= 9 – 4p – 12. – 4
= 9+ 16p + 48
-16p = 9 + 48
-16p = 57
P=