TN

cho ab+bc+ca=2017.Chung minh dang thuc sau:

(a2+2017)(b2+2017)(c2+2017)=(a+b)2(b+c)2(c+a)2

H24
25 tháng 10 2020 lúc 12:03

           Bài làm :

Ta có :

\(\left(a^2+2017\right)\left(b^2+2017\right)\left(c^2+2017\right)\)

\(=\left(a^2+ab+bc+ca\right)\left(b^2+ab+bc+ca\right)\left(c^2+ab+bc+ca\right)\)

\(=\left[\left(a^2+ab\right)+\left(bc+ca\right)\right]\left[\left(b^2+ab\right)+\left(bc+ca\right)\right]\left[\left(c^2+bc\right)+\left(ab+ca\right)\right]\)

\(=\left[a\left(a+b\right)+c\left(b+a\right)\right]\left[b\left(b+a\right)+c\left(b+a\right)\right]\left[c\left(c+b\right)+a\left(b+c\right)\right]\)\(=\left(a+b\right)\left(c+a\right)\left(a+b\right)\left(b+c\right)\left(b+c\right)\left(c+a\right)\)

\(=\left(a+b\right)^2\left(b+c\right)^2\left(c+a\right)^2\)

=> Điều phải chứng minh

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