设实数a,b,c,d,e满足(a+c)(a+d)=(b+c)(b+d)=e≠O,且a≠b,那么(a+c)(b+c)-(a+d)(b+d)=( )A.eB.2e
题型:单选题难度:简单来源:不详
设实数a,b,c,d,e满足(a+c)(a+d)=(b+c)(b+d)=e≠O,且a≠b,那么(a+c)(b+c)-(a+d)(b+d)=( ) |
答案
(a+c)(a+d)=(b+c)(b+d), (a+c)(a+d)-(b+c)(b+d)=0, a2+ad+ac+cd-b2-bd-bc-cd=0, a2+ad+ac-b2-bd-bc=0, a2-b2+ad-bd+ac-bc=0, (a-b)(a+b+c+d)=0. 因为a≠b,所以a+b+c+d=0, 那么(a+c)(b+c)-(a+d)(b+d), =ab+ac+bc+c2-ab-ad-bd-d2, =ac-ad+bc-bd+c2-d2, =( c-d)(a+b+c+d), =0. 故选C. |
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