Pls asap which relation is a function ?

What is the common difference in the following arithmetic sequence? 7,3,-1,-5

If sin θ=24/25 and 0 less than or equal to θ less than or equal to π/2, find the exact value of tan 2θ. answers; a) -527/336 b) -336/527 c)7/24 d) 24/7

What is the multiple zero and multiplicity of f(x) = (x ? 3)(x ? 3)(x + 5)? multiple zero is 3; multiplicity is 2 multiple zero is 5; multiplicity is 1 multiple zero is ? 5; multiplicity is 1 multiple zero is ? 3; multiplicity is 2