jika akar-akar persamaan kuadrat x² + bx - c = 0 adalah dua kali akar-akar persamaan kuadrat x² + x - (p/8 + 1/p) = 0, maka nilai dari -p² + 2pc + 4b = ...

x² + bx - c = 0,
x1 + x2 = -b/1 = -b
x1.x2 = -c/1 = -c

x² + x - (p/8 + 1/p) = 0
2x1 + 2x2 = -b
2(x1 + x2) = -b
2(-1/1) = -b
-2 = -b
b = 2
2x1.2x2 = -c
4(x1.x2) = -c
4(-(p/8 + 1/p)/1) = -c
-4(p/8 + 1/p) = -c
4(p²+8)/8p = c
(p²+8)/2p = c
p² + 8 = 2pc
8 = -p² + 2pc
-p² + 2pc = 8

-p² + 2pc + 4b
= 8 + 4(2)
= 8 + 8
= 16