What is word form and why do i have to write it in that type of form

Is this a polynomial function? i need to know asap

y=2x−1 5x−4y=1 is (1,1)(1,1) a solution of the system?

Will mark 50 show all what is the solution to the system of equations? use the substitution method and show your work. -5x+y= -3 -15 x+3y=7 explain what your answer in part (a) tells you about the association of the lines in this system.