Write the set using interval notation

Arley is building a model of a city map. in one part of the city, three roads form a right triangle, which harley draws as triangle abc, with the following measures: m∠b=90° and m∠a=30°. in his scale model, the hypotenuse of triangle abc, ac¯¯¯¯¯¯¯¯, has a length of 817−−√ cm. what is the value of a (the length of bc¯¯¯¯¯¯¯¯)?

Write a story that matches with the expression 42x-5 pls hurry

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?