Question

You reflect triangle PQR, with vertices P(-2, -4), Q(-3, -1), and R(-4, -4), across the y-axis to get triangle P′Q′R′. What are the coordinates of triangle P′Q′R′?

Answer 1

When you reflect something across the y axis, you take the opposite of all the x axis coordinates (the point 'on the other side of the number line,' and when they add together, they make 0). Now we can solve for each of the points.

Reflected across the y axis, we have to take the opposite of -2 and that's 2. That means that P becomes P'(2, -4).

Reflected across the y axis, we have to take the opposite of -3, and that's 3. That means that Q becomes Q'(3, -1).

Reflected across the y axis, we have to take the opposite of -4 and that's 4. That means that R becomes R'(4, -4)