Question

a  egal x apartine nr naturale divide 7≤x+5mai mic 15
b egal x apartine nr naturale divide 3 mai mic2x+1 mai mic 15

Answer 1

7≤x+5<15
a)7≤x+5
-x≤5-7
-x≤-2    (-1)
x≥2
x∈[2,+α)

x+5<15
x<15-5
x<10
x∈(-α,10)
sol este x∈[2,10)

b)3<2x+1<15
3<2x+1
-2x<1-3
-2x<-2         (-1)
x>2/2
x>1
x∈(1,+α)

2x+1<15
2x<15-1
x<14/2
x<7
x∈(-α,7)
sol.x∈(1,7)