Solving Quadratic Equations

1
The -b formula is used in the Junior Cycle at
Higher Level but also every level of the Leaving
Cert.
Remember Our Golden Rule
WHEN DO YOU HAVE TO USE IT?
2
Solving Quadratic Equationsx squared, xs,
number equals zero
1

Can we FACTORISE ?
Guide number 5 1x5
Add to 6 No Good
NO we cant
OOOPS! None Left
No factors of 5 will add to 7. So ..
We cannot use this method.
But is there another way to solve quadratic
equations .
We MUST use the b formula
3
1
So
This is the code that tells you that using
factors wont work so use the -b formula.
Do you see why you are asked to round off your
solutions?
4
SO I USE THE b FORMULA WHEN THE ROOTS HAVE TO BE
TO 1 OR 2 DECIMAL PLACES
Yes. I think so. And also when the roots have to
be in SURD form!
No. No. No. Its really EASY.
SURD form has put me in BAD form!
5
Solving Quadratic EquationsSolutions in SURD form
Lets look at the last equation we solved
Using the formula we got this
Told you it was EASY.
This is a SURD. It doesnt give you a nice whole
number.
So our solution is still in SURD form since
is there.
Heres our two solutions or roots or answers in
surd form
6
So
7
Same equation again but this time..
So
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WHAT YOU MUST KNOW
Golden Rule
x equals minus b plus or minus the square root
of b squared minus 4ac all over 2a
You MUST use the b formula when asked to give
the solutions
correct to 1 or 2 decimal places
OR
in SURD form
Now Practise the -b formula on these ones..
9
Solve these equations and give the roots correct
to 2 decimal places
QUADRATIC EQUATION ROOTS