Question

Persamaan kuadrat x² - 8x - 15 = 0 akar-akarnya adalah x1 dan x2. nilai 1/x1 + 1/x2 = ...

Answer 1

1/x1 + 1/x2 = -b/c = -(-8)/-15 = -8/15

Answer 2

x² - 8x - 15 = 0  a=1  b= -8   c= -15
x1+x2 = -b/a =-(-8)/1= 8
x1.x2 = c/a = -15/1 = -15

1/x1 + 1/x2 =1(x2)+1(x1) per x1.x2 (disamain penyebutnya, jadi x1.x2)
x1+x2/x1.x2 =-b/a per c/a = 8/-15 = -8/15