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Question : If x + y = √3 and x – y = √2, the value of 8xy(x2 + y2) is:

Option 1: 6

Option 2: √6

Option 3: 5

Option 4: √5


Team Careers360 16th Jan, 2024
Answer (1)
Team Careers360 18th Jan, 2024

Correct Answer: 5


Solution : According to the question,
x + y = √3
Squaring both sides, we get,
⇒ x 2 + y 2 + 2xy = 3 ––––––––––––(i)
Now, x – y = √2
Squaring both sides, we get,
⇒ x 2 + y 2 – 2xy = 2 ––––––––––––(ii)
Adding equations (i) and (ii), we get,
2x 2 + 2y 2 = 5
⇒ x 2 + y 2 = $\frac{5}{2}$ ––––––––––––––––(iii)
Now putting the value from equation (iii) in equation (i), we get,
$\frac{5}{2}$ + 2xy = 3
⇒ 2xy = 3 – $\frac{5}{2}$
⇒ 2xy = $\frac{1}{2}$
$\therefore$ xy = $\frac{1}{4}$
Now, the value of 8xy(x 2 + y 2 )
= $8 × \frac{1}{4} × \frac{5}{2}$
= $5$
Hence, the correct answer is 5.

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