At what angle does the line √3x + y − 5 = 0 meet the positive direction of the x-axis?

Correct answer: c 120°

y = −√3x + 5, so the slope −√3 = tan 120° and the angle is 120°.

Why the other options are wrong

• a 30°: y = −√3x + 5, so the slope −√3 = tan 120° and the angle is 120°. So 30° is not the answer.
• b 60°: 60° would need slope +√3; the slope −√3 is negative, so the angle is obtuse.
• d 150°: y = −√3x + 5, so the slope −√3 = tan 120° and the angle is 120°. So 150° is not the answer.