The value of (2 +√5 )( 2– √5 ) is
(a) 1 (b)-1 (c) 2 (d) none
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Answer:
b.-1
Step-by-step explanation:
(2+√5)(2-√5)=2^2-(√5)^2
=4-5
=-1 because of using formula a^2-b^2=(a+b)(a-b)
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