how to solve this equation: 3x^2-7x-10=0 with a quadratic formula

x =   [ −b  ± √  (b^2  − 4ac )]  2a       a =  3   b = −7  c =−10

x =  [ 7 ± √  (( −7)^2  − 4(3)(−10) ) ] / [ 2*3] 

x = [ 7 ± √ [49  + 120] ] / 6

x = [ 7 ± √ 169 ] / 6

x = [7 ±13 ]  / 6  

x = 20/6  =  10/3      and    x = −6/6  = −1