Soal Matematika Sukino Kelas X KTSP 2006 LKS 1 Bab 2 Bag B no 2

Latihan Kompetensi Siswa 1

Bab 2 : Persamaan dan Fungsi Kuadrat

Matematika Sukino Kelas X KTSP 2006

B.

2. Tuliskan masing-masing persamaan di bawah ini ke bentuk baku, kemudian hitunglah (a . b) dan (a . c).

a. 4x(x - 2) + 7 = 8 (x - 1)

b. (x + 2)/x = 6x / (x + 1)

c. 9y² = 4

d. 9t² = 10t

e. 2m² = 23m - 63

f. 1/x + 1/(x + 9) = 1/6

Jawaban :

a.

4x(x - 2) + 7 = 8 (x - 1)

4x² - 8x + 7 = 8x - 8

4x² - 8x - 8x + 7 + 8 = 0

4x² - 16x + 15 = 0

a = 4

b = -16

c = 15

a . b = 4 . - 16 = - 64

a . c = 4 . 15 = 60 

b. 

(x + 2)/x = 6x / (x + 1)

dikali silang

(x + 2)(x + 1) = 6x (x)

x² + 2x + x + 2 = 6x²

x² + 3x + 2 = 6x²

0 = 6x² - x² -  3x - 2

0 = 5x² -  3x - 2

a = 5

b = -3

c = -2

a . b = 5 . -3 = - 15

a . c = 5 . -2 = - 10

c.

9y² = 4

9y² - 4 = 0

a = 9

b = 0

c = -4

a . b = 9 . 0 = 0

a . c = 9 . -4 = - 36

d. 

9t² = 10t

9t² - 10t = 0

a = 9

b = -10

c = 0

a . b = 9 . -10 = - 90

a . c = 9 .0 = 0

e.

2m² = 23m - 63

2m² - 23m + 63 = 0

a = 2

b = -23

c = -63

a . b = 2 . -23 = - 46

a . c = 2 . -63 = - 126

f.

1/x + 1/(x + 9) = 1/6

samakan penyebut untuk ruas sebelah kiri

((x + 9)+ x) / (x (x +9)) = 1/6

(2x + 9) / (x² +9x) = 1/6

kali silang

6(2x + 9) = x² +9x

12x + 54 = x² +9x

0 = x² +9x - 12x - 54

0 = x² - 3x - 54

a = 1

b = -3

c = -54

a . b = 1 . -3 = -3

a . c = 1 . -54 = -54