the sum of a number and 20 times its reciprocal is 9. find the number?

6 ⤊

2007-12-01 01:40:30 · 3 answers · asked by jes 1 in Science & Mathematics ➔ Mathematics

x + 20/x = 9
x^2 - 9x + 20 = 0
(x - 5)(x-4) = 0

x = 4 or 5

2007-12-01 01:44:32 · answer #1 · answered by Dr D 7 · 3⤊ 4⤋

Let the no be X.
Then X+ 20/X=9.

X*2+20 =9X.

X*2 -9X +20=0, X*2 -5X-4X +20=0.
X( X-5) -4( X-5)=0. ( X-4) (X-5)=0.

X= 4 or5.

2007-12-01 06:38:28 · answer #2 · answered by Sasi Kumar 4 · 0⤊ 3⤋

x + 20/x = 9
xÂ² + 20 = 9x
xÂ² - 9x + 20 = 0
(x - 5) (x - 4) = 0
x = 5 , x = 4
ie two possible answers of 5 and 4.

2007-12-01 03:24:43 · answer #3 · answered by Como 7 · 3⤊ 2⤋