Hey man! So the form y - y1 = m (x - x1) is known as the Point Slope form, and is primarily used when you know the gradient and a point on the line, or want to write your answer in the form ay + bx + c = 0. y = mx + c is mostly used when you know the gradient and the y-intercept. As you yourself have noted, substituting into either of the two provide the same answer, so your answer is just as valid, meaning there's no need to worry unless the question has specifically asked for a certain form answer. If you're not used to using Point Slope, I'd suggest finding some questions on it to practice as we have seen it come up a few times in past papers.
Hey man! So the form y - y1 = m (x - x1) is known as the Point Slope form, and is primarily used when you know the gradient and a point on the line, or want to write your answer in the form ay + bx + c = 0. y = mx + c is mostly used when you know the gradient and the y-intercept. As you yourself have noted, substituting into either of the two provide the same answer, so your answer is just as valid, meaning there's no need to worry unless the question has specifically asked for a certain form answer. If you're not used to using Point Slope, I'd suggest finding some questions on it to practice as we have seen it come up a few times in past papers.