Solve the quadratic equation by using quadratic formula

show your work

a)x=6⁄7,   x= -1

b)x=6⁄7,   x=-6⁄7

c)x= 1,   x= -1

d)x= 1,   x=-6⁄7

e)x= 2,   x=-12⁄7

f)None of the above