a)5(x+1)-x>2(x+1) c)5x(2x+1)<10x(x+1)-1 e)(b-1)(b+1)≤b(b+2)
5x+5-x>2x+2 10x²+5x<10x²+10x-1 b²-1≤b²+2b
4x+5>2x+2 10x²+5x-10x²+10x+1<0 b²-1-b²+2b≤0
4x+5-2x-2>0 15x+1<0 -1+2b≤0
2x+3>0 15x<-1 2b≤1
2x>-3 x<-1/15 b≤0,5
x>-1,5 x∈(-∞;-1/15) b∈(-∞;0,5]
x∈(-1,5;+∞)
f)(k+2)(k-3)≥k(k+4)
k²-3k+2k-6≥k²+4k
k²-k-6≥k²+4k
k²-k-6-k²+4k≥0
3k-6≥0
3k≥6
k≥2
x∈[2;+∞)
