Question

下面计算(-7+a+b)(-7-a-a)正确的是

下面计算(-7+a+b)(-7-a-a)正确的是
a [-(7-a-b)][-(7+a+b)]=7²-a²-b²
b [-(7+a)+b][-(7+a)-b]=(7+a)²-b²
c -(7+a+b)[-7-(a+b)]=-7²-(a+b)²
d -(7+a+b)[-7-(a+b)]=7²-(a+b)²
若a+b=根号5，a-b=根号3，则ab=？？？
计算0.008^1340乘以[(-5)^2009]²

Answer 1

(-7+a+b)(-7-a-b)
=(7+a+b)[7-(a+b)]
=7²-(a+b)²

D正确

选D
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补充回答

ab=( (a+b)²-(a-b)² )/4=(5-3)/4=1/2
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接着答，完了给你加10分

追答

0.008^1340乘以[(-5)^2009]²
=0.008^1340乘以(-5)^4018
=0.008^1340乘以(-5)^(4020-2)
=0.008^1340乘以(-125)^1340乘以(-5)^(-2)
=(0.008×(-125))^1340乘以(-5)^(-2)
=1/25

Answer 2

b