Why is not possible to form a right triangle with the lengths 2, 4, and 7

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

50 plz, given the system of equations, match the following items. x + 3 y = 5 x - 3 y = -1 a) x-determinant b) y-determinant c) system determinant match the following to the pictures below.

Need so much on this one how many yards?