Question 347971
From {{{2x^2-8x-1}}} we can see that {{{a=2}}}, {{{b=-8}}}, and {{{c=-1}}}



{{{D=b^2-4ac}}} Start with the discriminant formula.



{{{D=(-8)^2-4(2)(-1)}}} Plug in {{{a=2}}}, {{{b=-8}}}, and {{{c=-1}}}



{{{D=64-4(2)(-1)}}} Square {{{-8}}} to get {{{64}}}



{{{D=64--8}}} Multiply {{{4(2)(-1)}}} to get {{{(8)(-1)=-8}}}



{{{D=64+8}}} Rewrite {{{D=64--8}}} as {{{D=64+8}}}



{{{D=72}}} Add {{{64}}} to {{{8}}} to get {{{72}}}



So the discriminant is {{{D=72}}}



Since the discriminant is greater than zero, this means that there are two real solutions.



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