4/7x+5/7x при x=5 1/4 ;9/3

To solve the expression \( \frac{4}{7}x + \frac{5}{7}x \) for \( x = 5 \frac{1}{4} \) and \( x = \frac{9}{3} \), we first need to simplify the expression.

1. Combine the like terms: \[ \frac{4}{7}x + \frac{5}{7}x = \frac{4 + 5}{7}x = \frac{9}{7}x \]

2. Convert \( 5 \frac{1}{4} \) to an improper fraction: \[ 5 \frac{1}{4} = 5 + \frac{1}{4} = \frac{20}{4} + \frac{1}{4} = \frac{21}{4} \]

3. Now substitute \( x = \frac{21}{4} \) into the expression \( \frac{9}{7}x \): \[ \frac{9}{7} \cdot \frac{21}{4} = \frac{9 \cdot 21}{7 \cdot 4} = \frac{189}{28} \] Simplifying \( \frac{189}{28} \):

   • The GCD of 189 and 28 is 7.
   • \( \frac{189 \div 7}{28 \div 7} = \frac{27}{4} \)

4. Next, substitute x = \( \frac{9}{3} = 3 \): \[ \frac{9}{7} \cdot 3 = \frac{27}{7} \]

So the results are:

• For \( x = 5 \frac{1}{4} \), the answer is \( \frac{27}{4} \).
• For \( x = \frac{9}{3} \), the answer is \( \frac{27}{7} \).