a) x² + 4x - 9 = 0
[tex]delta= b^{2} -4.a.c=
delta 4^{2} -4.1.(-9)=
delta=16+36=52
x1=-4-+ \sqrt{52} /2=2 \sqrt{52}
x2=-4-+ \sqrt{52} /2=2 \sqrt{52} [/tex]
b) x² + 15x - 4
[tex] b^{2} -4.a.c=
delta= 15^{2} -4.1.(-4)=
delta=225+16=241
x1=-15-+ \sqrt{241} /2
x2=-15-+ \sqrt{241}/2 [/tex]
