ABC is an equilateral triangle and AD is the altitude on BC. If the coordinates of A are (1, 2) and that of D are (-2, 6), then what is the equation of BC?

Slope of AD = (6-2)/(-2-1) = -4/3. BC is perpendicular to AD, so slope of BC = 3/4. BC passes through D(-2, 6): y - 6 = (3/4)(x + 2), so 4y - 24 = 3x + 6, giving 3x - 4y + 30 = 0. Hmm wait that's option (d). Let me recheck: 4(y-6) = 3(x+2), 4y - 24 = 3x + 6, 3x - 4y + 30 = 0. So answer is (d).