Найдите корень уравнения arccos4x+arccos2x=π/3

Cos (arccos4x+arccos2x) = cosπ/3

cos (arccos4x) cos (arccos2x) - sin (arccos4x) sin (arccos2x) = 1/2

4x*2x-√ (1-16x²) * √ (1-4x²) = 1/2

8x²-1/2=√ (1-20x²+64x^4)

64x^4-8x²+1/4=1-20x²+64x^4

20x²-8x²=3/4

12x²=3/4

x²=3/4:12

x²=1/16

x=-1/4

x=1/4