Solving the Square Root Equation: Find (x, y) for √x - √y = √(√61 - 6) and xy = 9

Radical Equations with Product Constraints

Solve the following system of equations:

{xy=616xy=9 \begin{cases} \sqrt{x}-\sqrt{y}=\sqrt{\sqrt{61}-6} \\ xy=9 \end{cases}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:13 Let's solve this system of equations together.
00:16 First, let's square the first equation. Great job!
00:20 We can use the special multiplication formulas to square it. Isn't that neat?
00:30 Now, take the square root of the second equation. You're doing well!
00:43 Substitute the second equation into the first. Keep going!
00:55 Let's simplify it whenever you can. Nice work!
01:01 Here, we find the expression for X. You're almost there!
01:08 Now, plug X back into the second equation to find Y. Keep it up!
01:13 Open those parentheses carefully, multiplying each term. You've got this!
01:22 Arrange the equation so it equals zero on one side. Nearly done!
01:26 Find the two solutions for Y. Excellent!
01:39 These are the solutions for Y. Good work!
01:46 Insert the solutions for Y back into the expression for X to find X. Keep going!
02:03 These are the possible solutions for X and Y. Well done!
02:07 And that is the solution to our problem! Excellent job!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following system of equations:

{xy=616xy=9 \begin{cases} \sqrt{x}-\sqrt{y}=\sqrt{\sqrt{61}-6} \\ xy=9 \end{cases}

2

Step-by-step solution

To solve the problem, we will proceed with the following steps:

  • Step 1: Calculate the value of 616\sqrt{\sqrt{61}-6}.
  • Step 2: Express y\sqrt{y} in terms of x\sqrt{x} using the first equation.
  • Step 3: Form a single-variable equation to solve for x\sqrt{x}.
  • Step 4: Back-substitute to find y\sqrt{y}.
  • Step 5: Use squaring to find xx and yy as needed.

Step 1: Compute 616\sqrt{\sqrt{61}-6}.

Calculate 616617.81\sqrt{61}-6 \to \sqrt{61} \approx 7.81 . Therefore, 6161.81\sqrt{61}-6 \approx 1.81. Thus 616=1.81\sqrt{\sqrt{61}-6} = \sqrt{1.81}. For efficacy, we solve further using variables.

Step 2: Using the equation xy=616\sqrt{x} - \sqrt{y} = \sqrt{\sqrt{61}-6}, let x=a\sqrt{x} = a and y=b\sqrt{y} = b with ab=ca-b = c and referred c as calculated.

Step 3: With ab=9=3 ab = \sqrt{9} = 3 (as xy=9xy = 9 hence xy\sqrt{x}\sqrt{y}), we substitute b=3ab = \frac{3}{a}.

Thus, a3a=616a - \frac{3}{a} = \sqrt{\sqrt{61} - 6}. Rearrange into: a2a6163=0 a^2 - a\sqrt{\sqrt{61} - 6} - 3 = 0 as a quadratic equation in aa.

Solving yields solutions for aa, use quadratic formula, or completing squares.

Solving, get solutions, a=6122.5a = \frac{\sqrt{61}}{2} - 2.5 and 612+2.5\frac{\sqrt{61}}{2} + 2.5

Backward solve bb by substituting values back.

Thus, for each aa, solve for xx or yy square them and check.

The solution is:

x=6122.5 x=\frac{\sqrt{61}}{2}-2.5 , y=612+2.5 y=\frac{\sqrt{61}}{2}+2.5 or x=612+2.5 x=\frac{\sqrt{61}}{2}+2.5 , y=6122.5 y=\frac{\sqrt{61}}{2}-2.5

Final solution:

x=6122.5 x=\frac{\sqrt{61}}{2}-2.5

y=612+2.5 y=\frac{\sqrt{61}}{2}+2.5

or

x=612+2.5 x=\frac{\sqrt{61}}{2}+2.5

y=6122.5 y=\frac{\sqrt{61}}{2}-2.5

3

Final Answer

x=6122.5 x=\frac{\sqrt{61}}{2}-2.5

y=612+2.5 y=\frac{\sqrt{61}}{2}+2.5

or

x=612+2.5 x=\frac{\sqrt{61}}{2}+2.5

y=6122.5 y=\frac{\sqrt{61}}{2}-2.5

Key Points to Remember

Essential concepts to master this topic
  • System Setup: Use substitution x=a \sqrt{x} = a and y=b \sqrt{y} = b to simplify
  • Key Relationship: From xy=9 xy = 9 , we get ab=3 ab = 3 , so b=3a b = \frac{3}{a}
  • Verification: Check both xy=9 xy = 9 and xy=616 \sqrt{x} - \sqrt{y} = \sqrt{\sqrt{61} - 6}

Common Mistakes

Avoid these frequent errors
  • Solving equations separately instead of as a system
    Don't solve xy=616 \sqrt{x} - \sqrt{y} = \sqrt{\sqrt{61} - 6} alone = infinite solutions! This ignores the constraint xy=9 xy = 9 which limits solutions to specific values. Always use both equations together by substitution to find the unique solution pair.

Practice Quiz

Test your knowledge with interactive questions

Solve the following exercise:

\( \sqrt{30}\cdot\sqrt{1}= \)

FAQ

Everything you need to know about this question

Why do we substitute x=a \sqrt{x} = a and y=b \sqrt{y} = b ?

+

This substitution simplifies the radical equation into a more manageable form. Instead of working with nested radicals, we get ab=616 a - b = \sqrt{\sqrt{61} - 6} and ab=3 ab = 3 , which is easier to solve!

How do I get from xy=9 xy = 9 to ab=3 ab = 3 ?

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Since a=x a = \sqrt{x} and b=y b = \sqrt{y} , we have ab=xy=xy=9=3 ab = \sqrt{x} \cdot \sqrt{y} = \sqrt{xy} = \sqrt{9} = 3 . This is a key property of radicals!

Why does this system have two solution pairs?

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When we solve the quadratic equation for a a , we get two values. Each value of a a gives a corresponding b b value, creating two valid (x,y) pairs that satisfy both original equations.

What if I get negative values under the square root?

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Always check that your final answers make mathematical sense! Since we're dealing with x \sqrt{x} and y \sqrt{y} , both x x and y y must be non-negative for real solutions.

How do I verify my final answer is correct?

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Substitute your (x,y) (x,y) values back into both original equations:

  • Check that xy=9 xy = 9
  • Check that xy=616 \sqrt{x} - \sqrt{y} = \sqrt{\sqrt{61} - 6}

If both are satisfied, your solution is correct!

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