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

Question

Solve the following system of equations:

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

Video Solution

Solution Steps

00:00 Solve the following system of equations
00:03 Square the first equation
00:07 Use the shortened multiplication formulas to square
00:17 Take the square root of the second equation
00:30 Substitute the second equation into the first
00:42 Simplify wherever possible
00:48 This is the expression for X
00:55 Insert the expression for X into the second equation to find Y
00:59 Open parentheses properly, making sure to multiply by each term
01:09 Arrange the equation so that the right side equals 0
01:13 Find the two solutions for Y
01:26 These are the solutions for Y
01:33 Insert these solutions into the expression for X to find the solutions for X
01:50 These are the possible solutions for X and Y
01:53 This is the solution

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

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