21. jika a dan b merupakan akar-akar persamaan kuadrat x² + x – 3=0, maka nilai 2a² + b² +a

x² + x – 3 = 0

x(1,2) =

-1+-√(1²-4.1.-3)/2.1 =

-1+-√(13)/2 =

x1 = a = (-1+√13)/2

x2 = b = (-1-√13)/2

2a² + b² + a =

2(-1+√13)/2)² + (-1-√13)/2)² + (-1+√13)/2 =

2(14-2√13)/4 + (14+2√13)/4+ (-1+√13)/2 =

(14-2√13)/2 + (14+2√13)/4 + (-1+√13)/2 =

(28-4√13 + 14+2√13 -2 + 2√13)/4 =

40/4 =

10