A polynomial expression is shown below. (a * x ^ 2 - 5)(3x ^ 4 + 2x ^ 2 + 6) - (21x ^ 6 + 12x ^ 3) The expression is simplified to: - x ^ 4 + 12x ^ 3 + 32x ^ 2 - 30 What is the value of a

What is the next step in the given proof? choose the most logical approach. a. statement: m 1 + m 2 + 2(m 3) = 180° reason: angle addition b. statement: m 1 + m 3 = m 2 + m 3 reason: transitive property of equality c. statement: m 1 = m 2 reason: subtraction property of equality d. statement: m 1 + m 2 = m 2 + m 3 reason: substitution property of equality e. statement: 2(m 1) = m 2 + m 3 reason: substitution property of equality