math
posted by peter on .
completing the square
3x^2 +15 33 =0
a=3
b=15
c=33
15+or sqrt2254*3*33/2*3
15+orsqrt225+396/6
is this right because don't you have to subtract not add the 396
please help. thanks

3x²+15x33
a=3, so
=3(x²+5x11)
=3[(x+2.5)²112.5²]
=3[(x+2.5)²(√(17.25))²]
=3(x+2.5+√(17.25))(x+2.5√(17.25)))
So
x=2.5±√(17.25)
which you can also express integers as follows:
x=[5±√(69)]/2