if a + b = 7 & about = 10 find a² + b²
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1
Answer:
Correct option is
D
±3
Given, (a+b)=7, ab=10
Squaring both sides
⇒(a+b)
2
=7
2
⇒a
2
+b
2
+2ab=49
⇒a
2
+b
2
=49−2(10)
⇒a
2
+b
2
=29
Now,
(a−b)
2
=a
2
+b
2
−2ab
=29−2(10)
=29−20
=9
∴a−b=
9
=±3
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