Help me please :)

1-for what value of x is line a parallel to line b 2-for what value of x is line a parallel to line b

What is the value of x when x + 7 = 21?

Factor the polynomial 4x4 – 20x2 – 3x2 + 15 by grouping. what is the resulting expression? (4x2 + 3)(x2 – 5) (4x2 – 3)(x2 – 5) (4x2 – 5)(x2 + 3) (4x2 + 5)(x2 – 3)