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how do i find the number of roots for a curve that has dy/dx

2x^4 -20x^2 + 50.

if i substitute y=x^2 and use the discriminant formula i get

b^2 - 4ac = 400 - 4 x 2 x 50

= 400 - 400

= 0

This way says there 1 root, answers say it has 2. Which method am i meant to use for this?

if i factorise i get 2(y-5)^2

which is also 1?

2x^4 -20x^2 + 50.

if i substitute y=x^2 and use the discriminant formula i get

b^2 - 4ac = 400 - 4 x 2 x 50

= 400 - 400

= 0

This way says there 1 root, answers say it has 2. Which method am i meant to use for this?

if i factorise i get 2(y-5)^2

which is also 1?

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