Solving In Terms Of Another Variable

The Desmos trick

Desmos graphs equations exactly as given — they don't need to be solved for y first. To find x given a y-value (or vice versa), graph the original equation plus a horizontal or vertical line at the known value, then click the intersection to read the other variable.

• Type the equation exactly as given, e.g. 2x + 5y = 20 — no need to isolate a variable
• To find x when y = k: graph the equation and y = k, then click the intersection
• To find y when x = k: graph the equation and x = k (a vertical line), then click the intersection
• For a formula with an unknown constant, add a slider for it and drag until the graph matches the given condition