Lucia made a mistake when she rewrote the formula
To rewrite the formula to x is a function of y. we have to add 2y to both sides of the formula. Instead of adding 2y, Lucia subtracted 2y from the right side.
Instead of what she did, x should be written the following way
To rewrite the formula to x is a function of y. we have to add 2y to both sides of the formula. Instead of adding 2y, Lucia subtracted 2y from the right side.
Instead of what she did, x should be written the following way