Which function is a quadratic function?
y – 3x2 = 3(x2 + 5) + 1
y2 – 7x = 2(x2 + 6) + 7
y – 2x2 = 6(x3 + 5) – 4
y – 5x = 4(x + 5) + 9

Astocks price gained 3% in april and 5% in may and then lost 4% in june and 1% in july during which month did the stocks price change the most