(x-2y-9)(x+2y-9)怎么解?(a+3b-c)^2这道题怎么解?两道题都要回答哦

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(x-2y-9)(x+2y-9)怎么解?(a+3b-c)^2这道题怎么解?两道题都要回答哦
(x-2y-9)(x+2y-9)怎么解?
(a+3b-c)^2这道题怎么解?两道题都要回答哦

(x-2y-9)(x+2y-9)怎么解?(a+3b-c)^2这道题怎么解?两道题都要回答哦
1、[(x-9)-2y][(x-9)+2y]
=(x-9)²-(2y)²
=x²-18y+81-4y²
2、[(a+3b)-c]²
=(a+3b)²-2c(a+3b)+c²
=a²+6ab+9b²-2ac-6bc+c²