the sum of the expanded angle is 180⇒

-2x^2(4x − 3)
=-8x^3 + 6x^2
hope it helps
I think 37%......................................................
30 plus EF = 180
Ef = 150
circumscribed angle plus the central angle is 180
You just need to plug those expressions inside the formula: it doesn't matter if they're expressions involving a variable instead of plain numbers: the formula becomes

If you want, you can simplify it by expanding the square and then multiply the two parenthesis:
