Persamaan kuadrat x kuadrat - 4x + 1 = 0 akar akarnya x1 dan x2.Persamaan kuadrat baru yg akar-akar'y 2x1 dan 2x2 adalah...

x^2 - 4x + 1

x1 + x2 = -b/a = 4
x1.x2 = c/a = 1

akar baru:
-b/a = 2x1 + 2x2 = 2(x1 + x2) = 2(4) = 8
c/a = 2x1.2x2 = 4(x1.x2) = 4(1) = 4

persamaan baru:
x^2 - (-b/a) + (c/a) =
x^2 - 8x + 4