5(2x-5)(x+1)=13
combine the parts in parentheses
5 (2x^2 +2x -5x -5) = 13
combine the terms in the middle
5 (2x^2 -3x -5) = 13
distribute the 5 into the parentheses
10x^2 -15x - 25 = 13
subtract 13 from both sides
10x^2 -15x -38 = 0
quadratic formula
(-(-15) +- Sqrt( (-15)^2 - 4(10)(-38) ) ) / 2(10)
(15 +- Sqrt( 225 + 1520) ) / 20
(15 +- Sqrt(1745) ) / 20
3/4 +- Sqrt(1745)/20
1745 factors to 5 * 349, so the square root doesn't simplify
Solution is x = 3/4 +- Sqrt(1745)/20