Jawab:

Tentukanlah hasil perkalian suku dua berikut ini, kemudian sederhanakanlah !

1 ) ( x – 5 ) ( x + 2 )

2 ) ( -4x + 3 ) ( x – 6 )

3 ) ( 4 + 3a ) ( a – 7 )

"Caranya"

1 ) ( x – 5 ) ( x + 2 ) = ( x – 5 )x + ( x – 5 )2

= x2 – 5x + 2x – 10

= x2 – 3x – 10

2) ( -4x + 3 ) ( x – 6 ) = ( -4x + 3 )x + ( -4x + 3 ) (-6)

= -4x2 + 3x + 24x – 18

= -4x2 + 27x – 18

3 ) ( 4 + 3a ) ( a – 7 ) = ( 4 + 3a )a + ( 4 + 3a )(-7)

= 4a + 3a2 – 28 -21a

= 3a2 – 17a – 28

4. 3 ( 2x+3)-2(4x-5)=

6x+9-8x+10

6x-8x+9+10

-2x+19

5. a. 2(a + b)

b. 3(a – c)

c. 2(2a + b)

d. 5(2a – c)

e. 8(4a – 3b)

f. -3(4a – 3b)

g. -4(5 + 2d)

h. (2a + 5)(a + 2)

i. (3x – 5)(x + 3)

j. (5x – 2)(x – 2)

Penyelesaian:

a. 2(a + b) = 2a + 2b

b. 3(a – c) = 3a – 3c

c. 2(2a + b) = 4a + 2b

d. 5(2a – c) = 10a – 5c

e. 8(4a – 3b) = 32a – 24b

f. -3(4a – 3b) = -12a + 9b

g. -4(5 + 2d) = -20 – 8d

h. (2a + 5)(a + 2) = 2a(a + 2) + 5(a + 2)

= 2a2 + 4a + 5a + 10

= 2a2 + 9a + 10

i. (3x – 5)(x + 3) = 3x(x + 3) – 5(x + 3)

= 3x2 + 9x – 5x – 15

= 3x2 + 4x – 15

j. (5x – 2)(x – 2) = 5x(x – 2) – 2(x – 2)

= 5x2 – 10x – 2x + 4

= 5x2 – 12x + 4

6. 5(a + 2b)

5(a + 2b) = (5 × a) + (5 × 2b) = 5a + 10b