6) k^2+k+1=13
or k^2+k -12=0
or k^2 + 4k -3k -12 =0
or k(k+4)-3(k+4)=0
or (k-3)(k+4)=0
so, k=3 or k= -4
7) 4a^2−a=3
4a^2 -a -3 =0
or 4a^2 -4a +3a -3 =0
or 4a(a-1) +3(a-1)=0
or (4a+3)(a-1) =0
So, a = -3/4 or a=1
8) w^2−4=0
or w^2 =4
or w = +/- sqrt(4)
So, w =2 or w= -2