In a absolute value graph the value of y is the same in -x and x.
Then if the coordinates (x,y) one point is (1, 8), the graph have another point in (- 1, 8).To find the value of a you use one of the points (x,y) in the general form of absolute value:
( 1 , 8) x=1 f(x)= y=8
[tex]8=a\lvert1\rvert[/tex]As:
[tex]\lvert\pm a\rvert=a[/tex]You get:
[tex]8=a\cdot1[/tex]Then:
[tex]a=8[/tex]The equation for the graph with points (1 , 8) and ( -1, 8) is:
[tex]f(x)=8\lvert x\rvert[/tex]a= 8