What is wrong with the following proof? Clearly we know that 1 does not equal 2. What rule of algebra did we break that makes this conclusion invalid? I've numbered the lines for you so you can refer to the line numbers in your explanation

The point a is at –2 and the point b is at 7. marissa would like to divide this line segment in a 4: 3 ratio, and she would like to use the formula x = (x2 – x1) + x1. what values should she substitute into the formula? a = a + b = x1 = x2 =