If (y + z) = 8 and yz = 6, find the value of (y - z)2.
- AOption (a)
36
- BOption (b)
40
- COption (c)
49
- DOption (d)
44
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Correct answer
40
Why this answer is correct
Given:
(y + z) = 8
(yz) = 6
(y - z)2 = ?
Concept used:
(x - y)2 = x2 + y2 - 2xy
(x + y)2 = x2 + y2 + 2xy
Calculations:
According to the question,
(y + z) = 8
Squaring on both sides,
⇒ (y + z)2 = (8)2
⇒ y2 + 2yz + z2 = 64
⇒ y2 + 2(6) + z2 = 64
⇒ y2 + 12 + z2 = 64
⇒ y2 + z2 = 64 - 12
⇒ y2 + z2 = 52
Now for (y - z)2
(y - z)2 = y2 + z2 - 2yz
⇒ (y - z)2 = 52 - 2(6)
⇒ (y - z)2 = 52 - 12
⇒ (y - z)2 = 40
∴ The value of (y - z)2 is 40.
Alternate Method(x - y)2 = (x + y)2 - 4xy
(y - z)2 = (y + z)2 - 4yz
(y - z)2 = (8)2 - 4 x 6
(y - z)2 = 40
