6, Prove that 5x4 + 2x3-1 is (x4) 7. Prove that x3 + 7x + 2 is (x3) 8, write the truth table for the proposition--(r -, q) v (p -r) . 9. Determine whether p (qr)and p- (q Ar) are equivalent 10. Determine whether this proposition is a tautology: ((p-*q)A p)q 11. Write the contrapositive, converse and the inverse of the following: If you try hard, then you will win