Please help!! ASAP
1) Prove that the equation 7x^(2)+bx−23=0 for any value of b has one positive and one negative root.

2) Prove that the equation 12x^(2)+70x+a2+1=0 for any value of a does not have any positive roots.

3) Prove that for any natural n the value of the expression (4n+5)^(2)–9 is divisible by 4.