$x^{2}$+ $2x$ - $3$ $=$ $0$$a$$=$$1$,$b$$=$$2$,$c$$=$$3$* Cách 1:$\Delta$$=$$b^2$$-$$4ac$$=$$2^2$$-$$4$$.$$1$$.$$(-3)$$=$$4$$+$$12$$=$$16$$>$$0$Phương trình có hai nghiệm phân biệt:$x_{1}$$=$$\frac{-b+\sqrt{\Delta}}{2a}$$=$$\frac{-2+\sqrt{16}}{2.1}$$=$$1$$x_{2}$$=$$\frac{-b-\sqrt{\Delta}}{2a}$$=$$\frac{-2-\sqrt{16}}{2.1}$$=$$3$*Cách 2:Vì:$a+b+c=1+2-3=0$Nên: $x_{1}=1, x_{2}=\frac{c}{a}= \frac{-3}{1}=-3$
$x^{2}$+ $2x$ - $3$ $=$ $0$$a$$=$$1$,$b$$=$$2$,$c$$=$$3$* Cách 1:$\Delta$$=$$b^2$$-$$4ac$$=$$2^2$$-$$4$$.$$1$$.$$(-3)$$=$$4$$+$$12$$=$$16$$>$$0$Phương trình có hai nghiệm phân biệt:$x_{1}$$=$$\frac{-b+\sqrt{\Delta}}{2a}$$=$$\frac{-2+\sqrt{16}}{2.1}$$=$$1$$x_{2}$$=$$\frac{-b-\sqrt{\Delta}}{2a}$$=$$\frac{-2-\sqrt{16}}{2.1}$$=$$3$*Cách 2:Vì:$a+b+c=1+2-3=0$Nên: $x_{1}=1, x_{2}=\frac{c}{a}= \frac{-3}{1}=-3$
$x^{2}$+ $2x$ - $3$ $=$ $0$$a$$=$$1$,$b$$=$$2$,$c$$=$$3$* Cách 1:$\Delta$$=$$b^2$$-$$4ac$$=$$2^2$$-$$4$$.$$1$$.$$(-3)$$=$$4$$+$$12$$=$$16$$>$$0$Phương trình có hai nghiệm phân biệt:$x_{1}$$=$$\frac{-b+\sqrt{\Delta}}{2a}$$=$$\frac{-2+\sqrt{16}}{2.1}$$=$$1$$x_{2}$$=$$\frac{-b-\sqrt{\Delta}}{2a}$$=$$\frac{-2-\sqrt{16}}{2.1}$$=$$3$*Cách 2:Vì:$a+b+c=1+2-3=0$Nên: $x_{1}=1, x_{2}=\frac{c}{a}= \frac{-3}{1}=-3$