Quadratic Formula answer help?

Question

2n^2 - 7n -30 = 0
2r^2 +2r - 40 = 0

Answer 1

 Comapre equation with standard from ax² + bx + c = 0.

Quadratic Formula: 

1) 2n^2-7n-30 = 0

Coefficients a =2,b = -7,c = -30   

n = (-(-7) (+/-)√(-7)^2-4*2*-30) /2*2

n = (7(+/-)√49+240) /4

n = (7(+/-)√289) /4

n = (7(+/-)17) /4

n = (7+17)/4      or         n = (7-17)/4

n = 24/4           or         n = -10/4

n = 6                or         n = -5/2

2) 2r^2+2r-40 = 0

Coefficients a = 2,b = 2, c = -40

r = (-2(+/-)√2^2 -4*2*-40)/2*2

r = (-2(+/-)√4+320)/4

r = (-2(+/-)√324)/4

r = (-2(+/-)18)/4

r = (-2+18)/4        or      r = (-2-18)/4

r = 16/4              or       r = -20/4

r = 4                  or      r = -5