Solve the equation: x+8/5 + x+5/x=1 and express the roots in the form a+bi?

2009-01-03 10:13 am

回答 (7)

2009-01-03 10:48 am
✔ 最佳答案
(x + 8)/5 + (x + 5)/x = 1
5x[(x + 8)/5 + (x + 5)/x] = 5x[1]
x(x + 8) + 5(x + 5) = 5x
x^2 + 8x + 5x + 25 = 5x
x^2 + 13x - 5x + 25 = 0
x^2 + 8x + 25 = 0
x = [-b ±√(b^2 - 4ac)]/2a

a = 1
b = 8
c = 25

x = [-8 ±√(64 - 100)]/2
x = [-8 ±√(-36)]/2
x = [-8 ±√(3^2 * i^2 * 2^2)]/2
x = [-8 ±6i]/2
x = -4 ±3i

∴ x = -4 ±3i
2016-04-01 4:57 pm
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5x - 5 = 3x + 12 5x - 3x = 5 + 12 2x = 17 x = 8.5
2014-10-07 10:24 pm
h
2009-01-03 10:32 am
-0.15 - 1.574i
-0.15 + 1.574i
2009-01-03 10:23 am
(x+8)/5 + (x+5)/x=1
multiply all by 5x
5x^2+8x + 5x+25=5x
5x^2+8x + 5x+25-5x=0
5x^2+8x +25=0
D=64-4*5*25=-440=440*i^2
x=(-8+/-2i√110)/5

If i've got it wrong, please put the brackets to see what is where
2009-01-03 10:21 am
Question looks as if it SHOULD be shown as :-

(x + 8) / 5 + (x + 5) / x = 1 ie NOT as given

x² + 8x + 5x + 25 = 5x
x² + 8x + 25 = 0
x = [ - 8 ± √ (64 - 100 ) ] / 2
x = [ - 8 ± √ (- 36) ] / 2
x = [ - 8 ± 6 i ] / 2
x = - 4 ± 3 i

PS
If I may offer some advice, questions should be clearly presented at this level.
Brackets are required.
Good luck!
2009-01-03 10:20 am
x^2++8x+25=0
x=-8+-sqrt(-36)/2
=-4+-6i


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