Answer:
A) 3
Step-by-step explanation:
<h2>Method 1)</h2>
Ques: 30/(4√3 + 3√2) = 4√3 - a√2
Rationalise the denominator.
→ 30/(4√3 + 3√2) × (4√3 - 3√2)/(4√3 - 3√2) = 4√3 - a√2
→ (120√3 - 90√2)/(48 - 18) = 4√3 - a√2
→ (120√3 - 90√2)/30 = 4√3 - a√2
→ 120√3 - 90√2 = 120√3 - 30a√2
→ 90√2 = 30a√2
On solving we get,
→ a = 3
<h2>Method 2)</h2>
Ques: 30/(4√3 + 3√2) = 4√3 - a√2
→ 30 = 4√3(4√3) + 4√3(-a√2) + 3√2(4√3) + 3√2(-a√2)
Solve the brackets,
→ 30 = 48 - 4a√6 + 12√6 - 6a
→ - 18 = - 4a√6 - 12√6 - 6a
Put like terms on one side,
→ - 18 + 6a = - 4√6 (a + 3)
Take the common,
→ 3(a - 3) = - 2√6 (a + 3)
→ 3 (a - 3) = 2√6 (-a - 3)
→ [3(a - 3)]/2√6 = - a - 3
Rationalise the denominator,
→ 2√6(3a - 9)/24 = - a - 3
→ (3a√6 - 9√6)/12 = - a - 3
→ √6(a - 3) = - 4a - 12
Do squaring on both sides,
→ [√6(a - 3)]² = - (4a + 12)²
→ 6(a² + 9 - 6a) = - (16a² + 144 + 96a)
Solve the brackets,
→ 6a² + 54 - 36a = - 16a² - 144 - 96a
→ 22a² - 132a + 198 = 0
→ 11a² - 66a + 99 = 0
→ a² - 6a + 9 = 0
Split the middle term,
→ a² - 3a - 3a + 9 = 0
→ a(a - 3) -3(a - 3) = 0
→ (a - 3)(a - 3) = 0
On comparing we get,
→ a = 3 (key to solve this and similar questions is rationalisation of the denominator)
Hence, the correct option is option A) 3.
