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I'm struggling with some questions on expanding surds in brackets and was wondering if anyone could help me out.

Here are the questions:
(√2+4)(√2+7)

(√5+2)(√5-9)

(9+√7)(9-√7)

Answer :

choixongdong
(√2+4)(√2+7)
= 2 + 4√2 + 7√2 + 28
= 30 + 11√2


(√5+2)(√5-9)
= 5 + 2√5 - 9√5 - 18
= -13 - 7√5

(9+√7)(9-√7)
= 81 - 7 

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