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Two positive real numbers have a sum of 5 and product of 5. Find the number.?
Two positive real numbers have a sum of 5 and product of 5. Find the number.
7 Answers
- Anonymous1 decade agoFavourite answer
Let
X = first number
Y = second number
X + Y = 5 -- Equation 1
XY = 5 -- Equation 2
From Equation 2, since Y = 5/X and substituting this into Equation 1,
X + 5/X = 5
Simplifying the above,
X^2 + 5 = 5X
X^2 - 5X + 5 = 0
Solving for the roots of the above using the quadratic formula,
X = [5 ± sqrt(5)]/2
and solving for Y,
Y = 5/X = 5/[5 ± sqrt(5)]/2
Y = 10/[5 ± sqrt(5)]
Hope this helps.
- Anonymous1 decade ago
Find two equations. To do this, asssign a random variable to your unknowns.
So two numbers sums equal 5? Then x+x=5 or 2x=5
Their products? y*y=5 or y^2=5
Solve for the equation and you will see the answer is 2 and 1/2
- notthejakeLv 71 decade ago
the two numbers are 2.5 + sqrt(5) / 2 and 2.5 - sqrt(5) / 2
two equations:
x + y = 5
xy = 5
rearranging the first equation:
y = 5 - x
sub into second equation
x(5 - x) = 5
5x - x^2 = 5
x^2 - 5x + 5 = 0
using the quadratic formula with a = 1, b = -5, and c = 5:
x = [5 +/- sqrt(5^2 - 4(5))] / 2
x = [5 +/- sqrt(5)] / 2, yielding the two positive numbers:
2.5 + sqrt(5) / 2 and 2.5 - sqrt(5) / 2
check: sum = 5 yep
(2.5 + sqrt(5)/2)(2.5 - sqrt(5) / 2) =
2.5^2 - 5/4 = 6.25 - 1.25 = 5 yep
- Chris SLv 51 decade ago
Since the numbers in question add up to 5, call them x and 5-x. Then make their product equal to 5:
x(5-x) = 5
Multiply it out and solve:
5x-x² = 5
x²-5x+5 = 0
x = (5屉(25-20)) / 2
x = 2.5±(â5)/2
Therefore, the numbers are approximately 1.4 and 3.6.
- whitesox09Lv 71 decade ago
Let the numbers be x and y.
x + y = 5
x*y = 5
Take the first equation:
x + y = 5
Subtract x from both sides:
y = 5 - x
Plug into other equation:
x(5 - x) = 5
Distribute x:
5x - x² = 5
Add x² and subtract 5x from both sides:
x² - 5x + 5 = 0
Apply the quadratic formula to solve for x:
x = [5 ± √((-5)² - 4(1)(5))]/((2)(1))
x = [5 ± √(25 - 20)]/2
x = [5 ± √(5)]/2
Find y:
y = 5 - x
y = 5 - [5 ± √(5)]/2
y = 10/2 - [5 ± √(5)]/2
y = [5 ± √(5)]/2
So x=y=[5 ± √(5)]/2
- ?Lv 61 decade ago
xy = 5....1
x+y = 5...2
x = 5/y
5/y + y = 5
5 + y^2 = 5y
y^2 -5y + 5 = 0
y1= 3.618
y2 = 1.381966
put y1 and y2 into 1