4) 4x²+30x-16=0
D=900+256=1156=34²
x1=-30+34/8 =4/8=1/2
x2=-30-34/8=-64/8=-8
lim(x->0,5) (x-1/2)(x+8) / 2(x-1/2) = x+8/2 = 0,5+8/2 =8,5/2 = 4,25
5)lim (x->1) (x-1)(x²+x+1)/(x-1) = lim (x->1) x²+x+1 = 1²+1+1=3
6)lim (x->0) (√(1+x) -1)(√(1+x)+1) / x*√(1+x)+1 =
=lim (x->0) (1+x-1) / x*√(1+x) +1 = lim (x->0) 1/√(1+x) +1 =
= 1/√1+0 +1 = 1/2