What is the equation of the function that is graphed as line a ? y = 3 x - 1
y = 3 x + 1
y = 1/3 x - 1
y = - 1/3 x + 1

1. ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2. subtraction property of equality 2. m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90 substitution 3. m∠1 + m∠2 = m∠3 + m∠2 definition of complementary 4. m∠1 = m∠3 given