# What is the focus and Directrix?

Plan

- 1 What is the focus and Directrix?
- 2 How do you find the focus and Directrix in standard form?
- 3 What is ellipse equation?
- 4 Where is the focus of a parabola?
- 5 How do you find the focus and directrix of a parabola on a calculator?
- 6 How do you find the vertex of a focus and Directrix?
- 7 What is p value in parabola?
- 8 How do you find the vertex in standard form?
- 9 How do you find standard form?
- 10 How do you convert standard form to vertex form on a calculator?
- 11 How do you write quadratic equations in standard form?
- 12 How are quadratic equations used in real life?
- 13 What does a quadratic equation look like on a graph?
- 14 How do you determine if a quadratic equation opens up or down?
- 15 How do you plot a quadratic graph?
- 16 How do you graph a standard form equation?
- 17 How do you convert Y intercept to standard form?
- 18 How do you rewrite an equation in standard form?
- 19 What are the rules of standard form?
- 20 What are standard form numbers?
- 21 Can a in standard form be negative?

## What is the focus and Directrix?

A parabola is set of all points in a plane which are an equal distance away from a given point and given line. The point is called the focus of the parabola, and the line is called the directrix . If the axis of symmetry of a parabola is vertical, the directrix is a horizontal line .

## How do you find the focus and Directrix in standard form?

The standard form is (x – h)2 = 4p (y – k), where the focus is (h, k + p) and the directrix is y = k – p. If the parabola is rotated so that its vertex is (h,k) and its axis of symmetry is parallel to the x-axis, it has an equation of (y – k)2 = 4p (x – h), where the focus is (h + p, k) and the directrix is x = h – p.

## What is ellipse equation?

The x-coordinates of the vertices and foci are the same, so the major axis is parallel to the y-axis. Thus, the equation of the ellipse will have the form. (x−h)2b2+(y−k)2a2=1 ( x − h ) 2 b 2 + ( y − k ) 2 a 2 = 1.

## Where is the focus of a parabola?

A parabola is set of all points in a plane which are an equal distance away from a given point and given line. The point is called the focus of the parabola and the line is called the directrix. The focus lies on the axis of symmetry of the parabola.

## How do you find the focus and directrix of a parabola on a calculator?

Parabola focus and directrix All you have to do is to use the following equations: Focus x-coordinate: x₀ = – b/(2a) ; Focus y-coordinate: y₀ = c – (b² – 1)/(4a) ; and. Directrix equation: y = c – (b² + 1)/(4a) .

## How do you find the vertex of a focus and Directrix?

In the equations y=a(x-h)^2+k and x=a(y-k)^2+h where a=1/4p , (h,k ) represents vertex and p is the distance between focus and vertex . In the above equations (a,b) represents FOCUS not VERTEX . In the first one directrix is y=k and in second one directrix is x=k .

## What is p value in parabola?

The absolute value of p is the distance between the vertex and the focus and the distance between the vertex and the directrix. (The sign on p tells me which way the parabola faces.) Since the focus and directrix are two units apart, then this distance has to be one unit, so | p | = 1.

## How do you find the vertex in standard form?

y=a(x−h)(x−h)+ky=ax2−2ahx+ah2+k . This means that in the standard form, y=ax2+bx+c , the expression −b2a gives the x -coordinate of the vertex.

## How do you find standard form?

The standard form for linear equations in two variables is Ax+By=C. For example, 2x+3y=5 is a linear equation in standard form. When an equation is given in this form, it’s pretty easy to find both intercepts (x and y). This form is also very useful when solving systems of two linear equations.

## How do you convert standard form to vertex form on a calculator?

How to convert from the standard form to the vertex form?

- Write the parabola equation in the standard form: y = a*x² + b*x + c ;
- Extract a from the first two terms: y = a * (x² + b/a * x) + c ;
- Complete the square for the expressions with x .

## How do you write quadratic equations in standard form?

A quadratic equation is an equation of the second degree, meaning it contains at least one term that is squared. The standard form is ax² + bx + c = 0 with a, b, and c being constants, or numerical coefficients, and x is an unknown variable.

## How are quadratic equations used in real life?

Quadratic equations are actually used in everyday life, as when calculating areas, determining a product’s profit or formulating the speed of an object. Quadratic equations refer to equations with at least one squared variable, with the most standard form being ax² + bx + c = 0.

## What does a quadratic equation look like on a graph?

The graph of a quadratic function is a U-shaped curve called a parabola. The sign on the coefficient a of the quadratic function affects whether the graph opens up or down. The x-intercepts are the points at which the parabola crosses the x-axis.

## How do you determine if a quadratic equation opens up or down?

There is an easy way to tell whether the graph of a quadratic function opens upward or downward: if the leading coefficient is greater than zero, the parabola opens upward, and if the leading coefficient is less than zero, the parabola opens downward.

## How do you plot a quadratic graph?

Have a go

- Click to see a step-by-step slideshow.
- Step 1 – The x axis goes from –2 to 2.
- Step 2 – Create a table for the x and y values that you will calculate to plot the graph.
- Step 3 – Find the values for y.
- Step 4 – Repeat this process for the remaining values, where x = -1, x = 0, x = 1 and x = 2.

## How do you graph a standard form equation?

First, find the intercepts by setting y and then x equal to zero. This is pretty straightforward since the line is already in standard form. Plot the x and y-intercepts, which in this case is (9, 0) and (0, 6) and draw the line on the graph paper!

## How do you convert Y intercept to standard form?

To convert from slope intercept form y = mx + b to standard form Ax + By + C = 0, let m = A/B, collect all terms on the left side of the equation and multiply by the denominator B to get rid of the fraction.

## How do you rewrite an equation in standard form?

The standard form of a linear equation is Ax+By=C A x + B y = C . Rewrite the equation with the sides flipped. Move all terms containing variables to the left side of the equation. Subtract y y from both sides of the equation.

## What are the rules of standard form?

The Standard Form for a linear equation in two variables, x and y, is usually given as Ax + By = C where, if at all possible, A, B, and C are integers, and A is non-negative, and, A, B, and C have no common factors other than 1.

## What are standard form numbers?

Any number that we can write as a decimal number, between 1.0 and 10.0, multiplied by a power of 10, is said to be in standard form. 1.98 ✕ 10¹³; 0.76 ✕ 10¹³ are examples of numbers in standard form.

## Can a in standard form be negative?

Standard Form of a Linear Equation A shouldn’t be negative, A and B shouldn’t both be zero, and A, B and C should be integers.