Question

C= 3x+5y/2y+9 + 2x-3y/5x-9 tại x+y=3

Tính C

 

Answer 1

Các bạn tính C giúp mình nhanh nhanh nhé

Answer 2

với x+y=3 thì:

C=\(\frac{3x+5y}{2y+9}+\frac{2x-3y}{5x-9}\)

=\(\frac{3x+3y+2y}{2y+9}+\frac{5x-3x-3y}{5x-9}\)

=\(\frac{3\left(x+y\right)+2y}{2y+9}+\frac{5x-3\left(x+y\right)}{5x-9}\)

=\(\frac{3.3+2y}{2y+9}+\frac{5x-3.3}{2x-9}\)

= 1+1

=2

Answer 3

\(C=\frac{3x+5y}{2y+9}+\frac{2x-3y}{5x-9}\)

\(\Rightarrow C=\frac{3x+3y+2y}{2y+9}+\frac{5x-3x-3y}{5x-9}\)

\(\Rightarrow C=\frac{3\left(x+y\right)+2y}{2y+9}+\frac{5x-3\left(x+y\right)}{5x-9}\)

\(\Rightarrow C=\frac{3.3+2y}{2y+9}+\frac{5x-3.3}{5x-9}\)

\(\Rightarrow C=\frac{9+2y}{2y+9}+\frac{5x-9}{5x-9}\)

\(\Rightarrow C=1+1=2\)

Vậy C = 2