-1/2ac+2a*a+ac-2ab-3/5a*a 其中a=5,b=4,c=2

(-1/2)ac+2a²+ac-2ab-(3/5)a²?
=(2-3/5)a²-2ab+(-1/2+1)ac
=(7/5)a²-2ab+(1/2)ac
=(7/5)*5²-2*5*4+(1/2)*5*2
=35-40+5
=0
5a*a-a-4+2a-4a*a
=(5-4)a²+(-1+2)a-4
=a²+a-4
=a²+a+1/4-1/4-4
=(a+1/2)²-1/4-4
=(-11/2+1/2)²-1/4-4
=(-5)²-1/4-4
=25-1/4-4
=21-1/4
=83/4
8p*p-7q-pq=6p-7p*p,(题目好像不完整)
8p²+7p²-6p-7q-pq=0
15p²-6p-7q-pq=0

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