Which shows a difference of squares?
10y^2 – 4x^2
16y^2 – x^2
8x^2 – 40x + 25
64x^2 – 48x + 9
10y^2 – 4x^2
16y^2 – x^2
8x^2 – 40x + 25
64x^2 – 48x + 9