Try this solution:
1. according to the condition

2. for more details see the attached graph.
Answer: [0;+oo)
The answer is 10 ft. make a triangle 6ft tall, 8ft long (90 degrees to the other line) and draw a line to complete the triangle. This is a type of 3,4,5 triangle, a 6,8,10. The other way to do it is sqrt(6^2+8^2) = sqrt(36+64) = sqrt (100) = 10.
Answer=4000ft
There are 3280.84 feet in 1 kilometer
1km=3280.84ft
4000ft >3280.84 ft
therefore, 4000ft is longer than 1 km
4000ft>1km
2x^2+2x-14x-7
Answer: 2x^2-12x-7