DDesmos SAT Prep
← All categories

Solving for Unknown Parameters

Find an unknown constant by making the graph fit a given condition.

The Desmos trick

When a problem gives you a function with an unknown constant plus one condition it must satisfy, create a slider for the constant and drag it until the graph passes through the required point — or just solve algebraically and confirm visually.

  • Type the function with the unknown left as a letter: y = a*x^2
  • Click the letter and choose 'add slider' to create a draggable parameter
  • Plot the required point and drag the slider until the curve passes through it

Practice questions

Q1The graph of y = ax^2 passes through the point (3, 18). What is the va…
Medium
Q2The function f(x) = x^2 + bx + 12 has a root at x = -4. What is the va…
Hard
Q3The graph of y = ax + 5 passes through the point (3, 11). What is the …
Medium
Q4The function f(x) = x^2 + bx - 5 has roots at x = -1 and x = 5. What i…
Hard