The sum of first an arithmatic sequence is 3n squared plus 4n what is first term

Select the correct answer. given: ∆abc with prove: statement reason 1. given 2. ∠cab ≅ ∠edb ∠acb ≅ ∠deb if two parallel lines are cut by a transversal, the corresponding angles are congruent. 3. ∆abc ~ ∆dbe aa criterion for similarity 4. corresponding sides of similar triangles are proportional. 5. ab = ad + db cb = ce + eb segment addition 6. substitution property of equality 7. division 8. subtraction property of equality what is the missing statement in the proof? scroll down to see the entire proof.