Can I get some help finding the x - intercept please? Thanks!
This can be solved using the quadratic formula:
Use the quadratic formula to find the x-values of the equation.
Simplify the radicand to get
Simplify the rest of the equation to get
Make sure you understand why you are doing this!
You are basically making the function equal to zero because whenever the function crosses the x axis, the x value is 0. Therefore, you are trying to find for what values the x equals zero.
This is effectively asking us to solve
The first way of trying to solve a quadratic equation is to factorise.
We need two numbers that sum to
In fact, there are no such numbers. So next, we turn to our two other ways of solving quadratic equations.
Method 1 - Completing the Square
This method is good if you don't have a calculator, and ideal if the coefficient of
Method 2 - The Quadratic Formula
A much better method if you have a calculator. Given the choice, the formula is a much better option.
This states that, for a quadratic
So for this example,
So which method is better to use? Factorising is the best method, although it is not always possible to factorise. Personally, the quadratic formula is the better method if you cannot factorise, since there are fewer steps involved compared to completing the square.
Can I factorise?
Look at the quadratic formula again.
The area under the square root sign can tell us about the nature of the solutions. This expression,
If a quadratic factorises, then
When we square root this, we get