Y = peso_laranja
X = diametro_laranja
n = np.size(X)
a = (n*np.sum(X*Y) - np.sum(X)*np.sum(Y))/(n*np.sum(X**2)-np.sum(X)**2)
b = np.mean(Y) - a*np.mean(X)
Y = peso_toranja
X = diametro_toranja
n = np.size(X)
a = (n*np.sum(X*Y) - np.sum(X)*np.sum(Y))/(n*np.sum(X**2)-np.sum(X)**2)
b = np.mean(Y) - a*np.mean(X)