here we're asked to solve this quadratic equation using the quadratic formula. Now the
first thing you have to do is put this
in standard form it has to look like ax
squared plus BX plus C okay in this case
equals zero in this case all i have to
do is subtract 4x and now it's in
standard form when it's in standard form
you can easily see a is 1 b is negative
4 and c is negative 9 and then you can
use the quadratic formula the quadratic
formula here gives the two solutions to
any quadratic equation in standard form
okay so in our case when we substitute
in the numbers negative negative 4 plus
or minus the square root negative 4
squared minus 4 times a times C all
divided by 2 times a simplifying
negative negative 4 is positive 4 plus
or minus the square root negative 4
squared is 16 plus 4 times 9 36 divided
by 2 okay so 4 plus or minus the square
root 52 all divided by 2 now we have to
simplify 52 52 is four times 13 so
thinking of it as 4 times 13 we can
rewrite that as 4 plus or minus two
square root of 13 okay square root of 4
is 2 and then break up that for action
to is a common denominator so for over 2
plus or minus 2 root 13 / 2 gives me my
final answer after I reduce to plus or
minus square root of 13 okay so the two
solutions here in set notation I can
write it as 2 plus or minus square root
of 13 knows there are two solutions
there
