1. segment ra=segment rb, rs||ab given 2. ∠a = ∠b base ∠'s of isosceles triangle = 3. ∠a = ∠2 if lines ||, corresponding ∠'s = 4. ∠b = ∠1 if lines ||, alternate interior ∠'s = 5. ∠1 = ∠2 substitution

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!