Which ordered pair is a reflection of (3,7) across the y-axis

Hello there! :D

When you reflect something on the y-axis, you flip the y-point. If it's positive, then make it negative. Vice versa. 

(3,7) (x,y) 7 is the point. Make it negative.

(3,7) => (3,-7) That is the point.

I hope this helps!
~kaikers

Abit confused about what you mean, but i think you might be referring to slope intercept form: y = mx + bin that case b, or the y intercept is already given.(0,-1)find the slope by using the formulay2 - y1/x2 - x1the final slope will be 4/2, equivalent to 2.now your equation should look like thisy = 4/2x -1sorry if this didn’t you out!