algebra2: how to solve equations by using quadratic formula
It is only for the quadratic equations [they have an x
2 term but no exponents (powers) higher than that] and they are equal to zero.
for example
5x
2-7x=12
I recognise that I can take all this to one side and have it equal to 0
5x
2-7x-12 = 0
Now that it is in the from
ax
2 + bx + c = 0 I can use the quadratic formula
a=5, b=-7, and c=-12
Look at this you tube clip it will help you remember the quadratic formula.
Just high light it and then right clip, then choose goto from the drop down menu
http://www.youtube.com/watch?v=O8ezDEk3qCg
the for the substitution of your question
ALWAYS write the formula first then
x ={ - -7 ± sqrt[ (-7)
2 - 4*5*-12 ] } / { 2 * 5 }
x = { 7 ± sqrt [ 49 + 240 ] } / 10
x = ( 7 ± sqrt [ 289 ] } / 10
The square root of 289 is 17. How is that for coincidence, I didn't do it on purpose
x = ( 7 ± 17 ) / 10
x = 24/10 OR x = -10/10
x = 2.4 or -1
If you substitute either of these values into the original equation it should make the equaation true. If not then I made a silly mistake somewhere.
Anyway I hope that helps. Make sure you look at the clip. That doesn't require much effort.
+118654 
