i need help with 5-10

5. Suppose you are trying to prove that f(x) is one-to-one by using contrapositive proof Which of the followings should be the last sentence of your proof? (A) Therefore Tz (B) Therefore 2 (C) Therefore f(z.)f(zz) for some (D) Therefore f(n) = f(ra) for some zi, 12 6. Suppose you are trying to prove the following Proposition: Proposition 2 : If a is an odd integer, then 2 +3a+5 is odd. Which method would you choose? (A) Direct Proof (B) Contrapositive Proof 7. Suppose you are trying to prove the following Proposition: Proposition 3 Suppose z, y Z If y+3) is even, then z is even or y is odd. Which method would you choose? (A) Direct Proof (B) Contrapositive Proof. 8. How many of the following statements is trae. * 1 8 mod 7 1 6 mod 7 * 12= 26 mod 7 e-8=-1 mod 7 (A) 1 (B) 2 (C) 3 (D) 4 9. Is the following Proposition true? b mod 6 then b mod 2 and a b mod 3. Proposition 4 : If (A) Yes (B) No 10 Is the converse of Proposition 4 m previous question true? (A) Yes (B) No