由a-b=b-c=3/5得 a-b=3/5..(1) b-c=3/5..(2) (1)+(2) a-b+b-c=3/5+3/5 a-c=6/5 ∴[a-b]^2+[a-c]^2+[b-c]^2=2[a^2+b^2+c^2]-2[ab+ac+bc] ∴[3/5]^2+[6/5]^2+[3/5]^2=2*1-2[ab+ac+bc] ∴ab+ac+bc=[2-54/25]/2=-2/25谢谢采纳!
采纳哦