Răspuns:
Explicație pas cu pas:
a)x²-9x+18=0
x1,2=9±√81-72/2=9±3/2 x1=9+3/2=12/2=6 x2=9-3/2=6/2=3
x1=9 ;x2=3
b)2x²-7x-4=0
x1,2=7±√49+32/4=7±9/4 x1=7+9/4=16/4=4 x2=-2/4=-1/2
x1=4 x2=-1/2
c)4x²-12x+9=0 (2x-3)²=0 x1,2=3/2
d)3x²+4x+5=0 x1,2=-2±√4-15/3 Δ<0 ecuatia Nu are solutii reale
