prove that the line with the equation

and the curve with equation

have no points of intersection

i started by putting the first equation into the second after making the first equation

. so it became

then expanded the brackets. so first i squared the first bracketed term and made it

then expanded the second and made it

so i was left with

which then came to

and used the discriminant theory to make sure it came to less than 0. i came up with

for the discriminant. so -80 was the discriminant. but my book says its -39. can someone explain where i went wrong with this? thanks