Could someone check my work? we're working on linear regression.

Which product is positive a is 2/5 -8/9 -1/3 -2/7 b is -2/5 8/9 -1/3 -2/7 c is 2/5 8/9 1/3 -2/7 d is -2/5 -8/9 1/3 2/7

Ahigh definition tv cost $800 with a down payment of 2/5 of the cost. how much is left to pay, in dollars after the down payment has been made?

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)