Challenge Question:

Given that [tex]\sqrt{6 - 4 \sqrt{2}} = \sqrt{a} - \sqrt{b}[/tex], find the value of [tex]a[/tex] and the value of [tex]b[/tex].



Answer :

Certainly! Let's tackle the problem step by step to find the values of [tex]\( a \)[/tex] and [tex]\( b \)[/tex] for the given expression [tex]\(\sqrt{6-4\sqrt{2}} = \sqrt{a} - \sqrt{b}\)[/tex].

1. Start with the given equation:
[tex]\[ \sqrt{6-4\sqrt{2}} = \sqrt{a} - \sqrt{b} \][/tex]

2. Square both sides to eliminate the square roots:
[tex]\[ ( \sqrt{6-4\sqrt{2}} )^2 = ( \sqrt{a} - \sqrt{b} )^2 \][/tex]
[tex]\[ 6 - 4\sqrt{2} = a + b - 2\sqrt{ab} \][/tex]

3. Separate the rational and irrational parts. Equate the rational parts and the irrational parts separately:

- The rational part: [tex]\[ 6 = a + b \][/tex]
- The irrational part: [tex]\[ -4\sqrt{2} = -2\sqrt{ab} \][/tex]

4. Simplify the irrational part equation:
[tex]\[ -4\sqrt{2} = -2\sqrt{ab} \][/tex]
[tex]\[ 4\sqrt{2} = 2\sqrt{ab} \][/tex]
[tex]\[ 2\sqrt{2} = \sqrt{ab} \][/tex]
[tex]\[ (2\sqrt{2})^2 = ab \][/tex]
[tex]\[ 8 = ab \][/tex]

5. Now we have a system of equations:
[tex]\[ \begin{cases} a + b = 6 \\ ab = 8 \end{cases} \][/tex]

6. Solve the system of equations:
To find [tex]\( a \)[/tex] and [tex]\( b \)[/tex], let's solve these two equations simultaneously.

- Let’s consider the quadratic equation that satisfies these conditions: [tex]\[ t^2 - (a+b)t + ab = 0 \][/tex]
Plugging in [tex]\( a+b = 6 \)[/tex] and [tex]\( ab = 8 \)[/tex]:
[tex]\[ t^2 - 6t + 8 = 0 \][/tex]

- Solve this quadratic equation using the quadratic formula [tex]\( t = \frac{-B \pm \sqrt{B^2 - 4AC}}{2A} \)[/tex]:
[tex]\[ t = \frac{6 \pm \sqrt{6^2 - 4 \cdot 1 \cdot 8}}{2 \cdot 1} \][/tex]
[tex]\[ t = \frac{6 \pm \sqrt{36 - 32}}{2} \][/tex]
[tex]\[ t = \frac{6 \pm \sqrt{4}}{2} \][/tex]
[tex]\[ t = \frac{6 \pm 2}{2} \][/tex]
So, we get two solutions: [tex]\[ t = \frac{6 + 2}{2} = 4 \quad \text{and} \quad t = \frac{6 - 2}{2} = 2 \][/tex]

7. Hence, the values of [tex]\( a \)[/tex] and [tex]\( b \)[/tex] are:
[tex]\[ a = 4, \quad b = 2 \quad \text{or} \quad a = 2, \quad b = 4 \][/tex]

So, the values of [tex]\( a \)[/tex] and [tex]\( b \)[/tex] are [tex]\( 2 \)[/tex] and [tex]\( 4 \)[/tex].