How to Solve a System of Equations with Square Roots?

  • MHB
  • Thread starter Albert1
  • Start date
In summary, "x,y ∈ R" means that x and y are both real numbers. To solve for x and y in an equation with two variables, you need two equations and can use methods such as substitution or elimination. In an equation with the condition "x,y ∈ R", x and y can be any real numbers, resulting in infinite possible solutions. Solving for x and y in an equation means finding the exact values that satisfy the equation, while finding the values that make the equation true means finding a set of values that make it a true statement. It is possible to solve for x and y in an equation with more than two variables, but you would need at least the same number of equations as variables to obtain a unique
  • #1
Albert1
1,221
0
$x,y\in R$
$find \,\ solution \,\,of \,\,x\,\, and\,\, y:$
$\left\{\begin{matrix}
x+y+\dfrac{9}{x}+\dfrac{4}{y}=10---(1)\\
(x^2+9)(y^2+4)=24xy---(2)
\end{matrix}\right.$
 
Mathematics news on Phys.org
  • #2
Albert said:
$x,y\in R$
$find \,\ solution \,\,of \,\,x\,\, and\,\, y:$
$\left\{\begin{matrix}
x+y+\dfrac{9}{x}+\dfrac{4}{y}=10---(1)\\
(x^2+9)(y^2+4)=24xy---(2)
\end{matrix}\right.$
One real solution: x=3, y=2
 
  • #3
My attempt:

From (2), we get ($x,y \ne 0$):\[xy\left ( x+\frac{9}{x} \right )\left ( y+\frac{4}{y} \right )=24xy\]

or

\[\left ( x+\frac{9}{x} \right )\left ( y+\frac{4}{y} \right )=24\].Let $a = x+\frac{9}{x}$ and $b = y+\frac{4}{y}$. Then the two equations read:\[a + b = 10\: \: \wedge \: \: ab = 24\]So either $a = 4$ and $b = 6$ or vice versa.Case I.
$a = 4$: The corresponding quadratic expression: $x^2-4x+9 = 0$, has no real roots and it makes no sense
to search for a y-root.Case II.
$a = 6$: The corresponding quadratic expression:$ x^2-6x+9 = (x-3)^2$.
$b = 4$: $y^2-4y+4 = (y-2)^2$.

Thus the only solution is the pair: $(x,y) = (3,2)$.
 
  • #4
Albert said:
$x,y\in R$
$find \,\ solution \,\,of \,\,x\,\, and\,\, y:$
$\left\{\begin{matrix}
x+y+\dfrac{9}{x}+\dfrac{4}{y}=10---(1)\\
(x^2+9)(y^2+4)=24xy---(2)
\end{matrix}\right.$
[sp]The left side of (2) is positive, so $x$ and $y$ are either both positive or both negative. If they are both negative then (1) cannot hold. So they are both positive.

Let $u = \sqrt x$, $v = \sqrt y.$ Then $$\Bigl(u - \dfrac3u\Bigr)^2 + \Bigl(v - \dfrac2v\Bigr)^2 = u^2 - 6 + \frac9{u^2} + v^2 - 4 + \frac4{v^2} = x+y+\dfrac{9}{x}+\dfrac{4}{y}-10 = 0.$$ Therefore $u - \dfrac3u = v - \dfrac2v = 0$, so that $x = u^2 = 3$ and $y = v^2 = 2.$[/sp]
 
Last edited:

FAQ: How to Solve a System of Equations with Square Roots?

What does "x,y ∈ R" mean?

"x,y ∈ R" means that x and y are both real numbers. In mathematics, the symbol "∈" is used to indicate membership in a set, and "R" represents the set of all real numbers.

How do you solve for x and y in an equation with two variables?

To solve for x and y in an equation with two variables, you need to have two equations. You can then use algebraic methods such as substitution or elimination to find the values of x and y that satisfy both equations.

Can x and y be any real numbers in this equation?

Yes, x and y can be any real numbers in an equation with the condition "x,y ∈ R". This means that there are infinite possible solutions for x and y in the given equation.

What is the difference between solving for x and y in an equation and finding the values of x and y that make the equation true?

Solving for x and y in an equation means finding the exact values of x and y that satisfy the equation, while finding the values of x and y that make the equation true means finding a set of values that make the equation a true statement.

Can you solve for x and y in an equation with more than two variables?

Yes, it is possible to solve for x and y in an equation with more than two variables. However, you would need at least the same number of equations as variables to obtain a unique solution for x and y. Otherwise, there would be infinite possible solutions.

Similar threads

Replies
3
Views
953
Replies
7
Views
1K
Replies
1
Views
2K
Replies
8
Views
1K
Replies
6
Views
955
Replies
2
Views
867
Replies
3
Views
1K
Replies
1
Views
1K
Replies
2
Views
964
Back
Top