SOLUTION: Hi, I do not understand how to reduce or when to reduce the fraction within the quadratic equation. I came up with this answer. Would you please show me how to reduce for the fin

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Hi, I do not understand how to reduce or when to reduce the fraction within the quadratic equation. I came up with this answer. Would you please show me how to reduce for the fin      Log On


   

Question 411026: Hi, I do not understand how to reduce or when to reduce the fraction within the quadratic equation. I came up with this answer. Would you please show me how to reduce for the final answer? Thanks.
-x^2+6x-21=0
(-1)-x^2+6x-21=0(-1)
x^2+6x-21=0
-6+-sqrt((6)^2-4(1)(-21))/2(1)
-6+-sqrt(36+84)/(2)
-6+-sqrt(120)/(2)
-6+-sqrt(6(20))/(2)
-6+-sqrt(6)/(2)
-6+- 20 sqrt(6)/(2)
-?+- sqrt(6)/(10) (thought we divide -6/20 then divide 2/20) leaves the 6
Found 2 solutions by edjones, ewatrrr:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
a=-1, b=6, c=-21
x=(-6+-sqrt(36-4*21))/-2 not /2 and not -4(1)(-21) should be -4(-1)(-21)
=(-6+-sqrt(-48))/-2
=(-6+-4sqrt(3)i)/-2
=3+-2sqrt(3)i
=3+2sqrt(3)i, =3-2sqrt(3)i
.
Ed

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

As important as correctly using the quadratic formula is starting with the

correct quadratic equation to apply it to:

-x^2+6x-21=0    |Must multiply ALL terms by -1 to proceed in tha fashion

 x^2 - 6x + 21 = 0

x+=+%286+%2B-+sqrt%28+-48+%29%29%2F%282%29+

x+=+%286+%2B-+sqrt%28+-16%2A3+%29%29%2F%282%29+

x+=+%286+%2B-+4i%2Asqrt%28+3+%29%29%2F%282%29+

x+=+%283+%2B-+2i%2Asqrt%28+3+%29%29+



x^2+6x-21=0   |If... this were the correct quadratic (using as an example)

-6+-sqrt(120)/(2)

-6+-sqrt(4*30)/(2)

-6+-2sqrt(30)/(2)

-3+-sqrt(30)   |important to take the 'sqrt(4)out front'