Discover the Symmetrical Axis in -3x^2 + 3: A Quadratic Analysis

Axis of Symmetry with Simplified Quadratics

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=3x2+3 f(x)=-3x^2+3

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the axis of symmetry for the function
00:03 The axis of symmetry is the X value at the vertex point
00:06 The point where if you fold the parabola in half, both halves are identical
00:09 Let's look at the function's coefficients
00:21 We'll use the formula to calculate the vertex point
00:32 We'll substitute appropriate values according to the given data and solve for X at the point
00:43 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=3x2+3 f(x)=-3x^2+3

2

Step-by-step solution

To find the axis of symmetry for the quadratic function f(x)=3x2+3 f(x) = -3x^2 + 3 , we follow these steps:

  • Identify coefficients: Here, a=3 a = -3 , b=0 b = 0 , and c=3 c = 3 .
  • Use the axis of symmetry formula for a quadratic ax2+bx+c ax^2 + bx + c given by x=b2a x = -\frac{b}{2a} .
  • Substitute b=0 b = 0 and a=3 a = -3 into the formula: x=02×(3) x = -\frac{0}{2 \times (-3)} .
  • This simplifies to x=0 x = 0 .

The axis of symmetry for the quadratic function f(x)=3x2+3 f(x) = -3x^2 + 3 is therefore x=0 x = 0 .

3

Final Answer

x=0 x=0

Key Points to Remember

Essential concepts to master this topic
  • Formula: Use x=b2a x = -\frac{b}{2a} for standard form ax2+bx+c ax^2 + bx + c
  • Technique: When b = 0, the axis becomes x=02a=0 x = -\frac{0}{2a} = 0
  • Check: Verify symmetry: f(1)=f(1)=0 f(-1) = f(1) = 0 confirms x=0 x = 0 is correct ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting the coefficient b equals zero
    Don't assume b = 1 when there's no x term = wrong axis calculation! Missing that b = 0 in f(x)=3x2+3 f(x) = -3x^2 + 3 leads to incorrect substitution in the formula. Always identify all coefficients: a = -3, b = 0, c = 3 before using x=b2a x = -\frac{b}{2a} .

Practice Quiz

Test your knowledge with interactive questions

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

\( f(x)=-3x^2+3 \)

FAQ

Everything you need to know about this question

Why is the axis of symmetry x = 0 and not x = 3?

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The axis of symmetry depends on the coefficient of x, not the constant term. Since there's no x term in f(x)=3x2+3 f(x) = -3x^2 + 3 , we have b = 0, making the axis x=0 x = 0 .

How can I visualize this parabola?

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This parabola opens downward (because a = -3 is negative) with its vertex at (0, 3). It's symmetric about the y-axis, so points like (-2, -9) and (2, -9) are equidistant from the axis.

What if the quadratic has an x term?

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When there's an x term, b ≠ 0, so you'll get a different axis. For example, in f(x)=3x2+6x+3 f(x) = -3x^2 + 6x + 3 , the axis would be x=62(3)=1 x = -\frac{6}{2(-3)} = 1 .

Does the negative coefficient affect the axis of symmetry?

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No! The sign of coefficient a only determines if the parabola opens up or down. The axis formula x=b2a x = -\frac{b}{2a} works the same regardless of whether a is positive or negative.

How do I check if my axis is correct?

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Pick two points equidistant from your axis and verify they give the same y-value. For x=0 x = 0 : try x = -1 and x = 1. Both give f(1)=f(1)=0 f(-1) = f(1) = 0 !

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