If a2 + b2 = 80 and a - b = 4, then ab = ?A. 20B. 24C. 28D. 321. C

1.	If a2 + b2 = 80 and a - b = 4, then ab = ?A. 20B. 24C. 28D. 321. C2. A3. D4. B
Answer» Correct Answer - Option 3 : D Given: a2 + b2 = 80 a – b = 4 Formula used: (a – b)² = a² + b² – 2ab Calculation: a – b = 4 ⇒ (a – b)² = 4² [Squaring both sides] ⇒ a2 + b2 – 2ab = 16 ⇒ 80 – 2ab = 16 ⇒ -2ab = 16 – 80 ⇒ -2ab = -64 ⇒ ab = 32 ∴ The value of ab is 32.

If a2 + b2 = 80 and a - b = 4, then ab = ?A. 20B. 24C. 28D. 321. C2. A3. D4. B

Answer» Correct Answer - Option 3 : D

Given:

a2 + b2 = 80

a – b = 4

Formula used:

(a – b)² = a² + b² – 2ab

Calculation:

a – b = 4

⇒ (a – b)² = 4² [Squaring both sides]

⇒ a2 + b2 – 2ab = 16

⇒ 80 – 2ab = 16

⇒ -2ab = 16 – 80

⇒ -2ab = -64

⇒ ab = 32

∴ The value of ab is 32.

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If a2 + b2 = 80 and a - b = 4, then ab = ?A. 20B. 24C. 28D. 321. C2. A3. D4. B

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