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Algebra I: Quadratic equations

Grade 10 · Math · Free lesson

Hey there! Ready to level up your algebra skills? Today, we are going to explore quadratic equations—the math behind the beautiful curves of throwing a basketball or launching a rocket!

In math, a quadratic equation is any equation that can be rearranged into a special standard form: ax² + bx + c = 0. The most important rule is that 'a' cannot be zero, which means we must always have an x² term!

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When you graph a linear equation (like y = mx + b), you get a straight line. But when you graph a quadratic equation, you get a beautiful, symmetrical U-shape called a parabola!

Vertex (Peak)

The goals of solving a quadratic equation are to find the 'roots' or 'x-intercepts'. These are the exact spots where our U-shaped curve crosses the horizontal x-axis (where y = 0).

x-axis Root 1 Root 2
✏️ Worked example

Solve the simple quadratic equation: x² - 9 = 0

  1. Identify the equation: x² - 9 = 0. Our goal is to isolate x.
  2. Add 9 to both sides of the equation to get x² by itself: x² = 9.
  3. Take the square root of both sides: x = ±√9.
  4. Remember that both a positive and a negative number squared equal a positive number (3 * 3 = 9 and -3 * -3 = 9).
  5. Write your two solutions: x = 3 and x = -3.
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