the first thing I'd do would be to reduce this equation. Divide all terms by 2:
-10x^2 + 13x + 3 = 0
Then I'd use the quadratic formula. The roots would be
-13 plus or minus sqrt(169-4(-10)(3) )
x = -----------------------------------------------------
-20
Can you simplify this? Hint: sqrt(289) = plus or minus 17.