1.(×+2) (×+5)=0 2.(×+4) (2×-5)=0 3.(3y+8^)=0 4.(×+1/2) (x-9)=0

1). (x + 2)(x + 5) 
= x² + 5x + 2x + 10
= x² + 7x + 10

2). (x + 4)(2x - 5)
= 2x² - 5x + 8x - 20
= 2x² + 3x - 20

3). Soal membingungkan ?

4). (x + 1/2)(x - 9)
= x² - 9x + 1/2x - 9/2
= x² - 17/2x - 9/2 ----->> (sama" dikali 2)
= 2x² - 17x - 9