Question

Giả sử a,b,c là các số thỏa mãn a+b+c = 259 và \(\frac{1}{a+b}+\frac{1}{b+c}=\frac{1}{a+c}=15\). Khi đó giá trị biểu thức Q = \(\frac{a}{b+c}+\frac{b}{a+c}+\frac{c}{a+b}\)

Answer 1

\(Q=\frac{a}{b+c}+\frac{b}{a+c}+\frac{c}{a+b}\)

\(Q=\left(\frac{a}{b+c}+1\right)+\left(\frac{b}{a+c}+a\right)+\left(\frac{c}{a+b}+1\right)-3\)

\(Q=\frac{a+b+c}{b+c}+\frac{a+b+c}{a+c}+\frac{a+b+c}{a+b}-3\)

\(Q=\left(a+b+c\right).\left(\frac{1}{b+c}+\frac{a}{a+c}+\frac{a}{a+b}\right)-3\)

\(Q=259.15-3\)

\(Q=3882\)

Vậy \(Q=3882\)

Answer 2

\(Q+3=\left(\frac{a}{b+c}+1\right)+\left(\frac{b}{a+c}+1\right)+\left(\frac{c}{a+b}+1\right)\)

\(=\frac{a+b+c}{b+c}+\frac{a+b+c}{a+c}+\frac{a+b+c}{a+b}\)

\(=\left(a+b+c\right)\left(\frac{1}{b+c}+\frac{1}{a+c}+\frac{1}{a+b}\right)\)

\(=259.15=3885\)

\(\Rightarrow Q=3885-3=3882\)

Answer 3

đề sai