SOLUTION: Hi, I want to know if this is correct please. x^2+20=8x I have to type the answer in a+bi form, which I am not sure if this is right or I have to put the * sign before the i.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: Hi, I want to know if this is correct please. x^2+20=8x I have to type the answer in a+bi form, which I am not sure if this is right or I have to put the * sign before the i.       Log On


   

Question 607536: Hi,
I want to know if this is correct please.
x^2+20=8x
I have to type the answer in a+bi form, which I am not sure if this is right or I have to put the * sign before the i.
x= 8+4i/2, 8-4i/2
Thanks,
Answer by alicealc(293) About Me  (Show Source):
You can put this solution on YOUR website!
no, you don't need to put * sign before the i
x%5E2%2B20=8x
x%5E2-8x%2B20=0
Use the formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a = 1, b = -8, c = 20
x+=+%28-%28-8%29+%2B-+sqrt%28+%28-8%29%5E2-4%2A1%2A20+%29%29%2F%282%2A1%29+
x+=+%288+%2B-+sqrt%28+64-80+%29%29%2F%282%29+
x+=+%288+%2B-+sqrt%28+-16+%29%29%2F%282%29+
x+=+%288+%2B-+sqrt%28+16%2A%28-1%29+%29%29%2F%282%29+
x+=+%288+%2B-+4i%29%2F%282%29+
so, the answer is:
x+=+%288+%2B+4i%29%2F%282%29+ or x+=+%288+-+4i%29%2F%282%29+
x+=+4+%2B+2i+ or x+=+4+-+2i+

So, there are 2 solutions.
You could put the solution into a + bi form in which
a = 4, b = 2 for the answer x = 4 + 2i
and
a = 4, b = -2 for the answer x = 4 - 2i (this is the same as x = 4 + (-2)i)