Jawabanmu

2014-05-20T13:32:14+07:00
a.x²+3x-15=0 ⇔ x1,2 = (-3 +- √(9 + 60))/2 = (-3 +-√69)/2
b.2x² - 5x=0 ⇔x(2x - 5) = 0 ⇔ x = 0 atau 2x = 5 ⇔ x = 5/2
c.9-x² = 0
⇔ (3-x)(3+x) = 0 ⇔ x = 3 atau x = -3