Determine the roots of each quadratic equation
a) k^(2) - 5k= 0
b) 9x^(2)=x+8
c) (8/3)t+5=(-1/3)t^(2)
d)(25/49)y^(2)-9=0

e) 2s^(2)-4s = 70
f) 4q^(2) - 28q =-49