Theo đề bài, ta có:
4y=5z
=> z= \(\frac{4}{5}\)y
Ta có:
2x+ 3y- 4z = 56
3y+ 3y- 4.\(\frac{4}{5}\)y=56
6y- \(\frac{8}{5}\)y = 56
\(\frac{22}{5}\)y = 56
=> y= \(\frac{140}{11}\)
=> x=\(\frac{3y}{2}\)= \(\frac{3.\frac{140}{11}}{2}\) =\(\frac{210}{11}\)
z= \(\frac{4y}{5}\)= \(\frac{4.\frac{140}{11}}{5}\) =\(\frac{120}{11}\)
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