If x = 2 3+ √7 , then ( − 3) 2 = a) 7 (b) 3 (c) 6 (d) none of these
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2
Final answer:
a) 7
kindly refer the attachment
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Answer:
The correct option is A
7
x
=
2
3
+
√
7
=
2
(
3
−
√
7
)
(
3
+
√
7
)
(
3
−
√
7
)
(Rationalising the denominator)
=
2
(
3
−
√
7
)
(
3
)
2
−
(
√
7
)
2
=
2
(
3
−
√
7
)
9
−
7
=
2
(
3
−
√
7
)
2
=
3
−
√
7
Now,
x
−
3
=
3
−
√
7
−
3
=
−
√
7
∴
(
x
−
3
)
2
=
(
−
√
7
)
2
=
7
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