5. If a + b = 7 and ab = 10; find a - b.
6. If a - b = 7 and ab = 18; find a + b.
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Answers :
Q.5) ==⟩⟩ 3
Q.6) ==⟩⟩ ±11
Step by step explanation :
Q.5) a + b = 7
ab = 10
a - b = ?
We know that,
(a + b)² = (a - b)² + 4ab
(7)² = (a - b)² + 4 × 10
49 = (a - b)² + 40
9 = (a - b)²
√9 = (a - b)
3 = a - b
Value of a - b = 3
_________________________
Q.6) a - b = 7
ab = 18
a + b = ?
We know that,
(a + b)² = (a - b)² + 4ab
(a + b)² = (7)² + 4 × 18
(a + b)² = 49 + 72
(a + b)² = 121
(a + b) = √121
(a + b) = ±11
Value of a + b = ±11
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