Mathematics Grade 11 15 min

Complete the square

Complete the square

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1

Introduction & Learning Objectives

Learning Objectives Transform a quadratic function from standard form, `ax^2 + bx + c`, to vertex form, `a(x-h)^2 + k`. Solve any quadratic equation by completing the square, finding both real and complex roots. Identify the vertex and axis of symmetry of a parabola directly from the vertex form of its equation. Derive the quadratic formula by applying the completing the square method to the general quadratic equation `ax^2 + bx + c = 0`. Handle cases where the leading coefficient `a` is not 1 and the linear coefficient `b` is an odd number. Apply the method of completing the square to find the center and radius of a circle given its general form equation. How can you find the exact center and radius of a circle from an equation like `x^2 + y^2 - 8x + 2y - 8 = 0`? 🎯 This po...
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Key Concepts & Vocabulary

TermDefinitionExample Standard Form of a QuadraticA quadratic function written as `f(x) = ax^2 + bx + c`, where `a`, `b`, and `c` are constants and `a ≠ 0`.`y = 2x^2 - 12x + 10` is in standard form. Vertex Form of a QuadraticA quadratic function written as `f(x) = a(x-h)^2 + k`, where `(h, k)` is the vertex of the parabola.`y = 2(x-3)^2 - 8` is in vertex form. The vertex is at `(3, -8)`. Perfect Square TrinomialA trinomial that can be factored into the square of a binomial. It follows the pattern `A^2 + 2AB + B^2 = (A+B)^2` or `A^2 - 2AB + B^2 = (A-B)^2`.`x^2 + 10x + 25` is a perfect square trinomial because it factors to `(x+5)^2`. Vertex of a ParabolaThe point where the parabola reaches its maximum or minimum value. In vertex form `a(x-h)^2 + k`, the vertex is `(h, k)`.For the parabola...
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Core Formulas

The Term to Complete the Square For an expression `x^2 + bx`, the term needed to create a perfect square trinomial is `(b/2)^2`. Take the coefficient of the x-term (`b`), divide it by 2, and square the result. This 'magic number' is what you add to complete the square. Perfect Square Trinomial Factoring Pattern `x^2 + bx + (b/2)^2 = (x + b/2)^2` Once you've added the correct term, the resulting trinomial will always factor into a binomial squared. The term inside the binomial is always `x` plus half of the original `b` coefficient.

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Sample Practice Questions

Challenging
When deriving the quadratic formula from `ax^2 + bx + c = 0`, the step `(x + b/2a)^2 = (b^2 - 4ac) / 4a^2` is reached. If `b^2 - 4ac = 0`, what does this imply about the solution for `x` and the graph of `y = ax^2 + bx + c`?
A.There are two distinct real solutions, and the parabola intersects the x-axis twice.
B.There is exactly one real solution, and the vertex of the parabola is on the x-axis.
C.There are two complex solutions, and the parabola does not intersect the x-axis.
D.There are no solutions, and the parabola is entirely above or below the x-axis.
Easy
To complete the square for the expression `x^2 + 14x`, what number must be added?
A.7
B.14
C.49
D.196
Easy
What is the vertex of the parabola given by the equation `f(x) = 3(x - 5)^2 + 8`?
A.(-5, 8)
B.(5, 8)
C.(3, 5)
D.(5, -8)

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