Question

Hay que encontrar las incógnitas
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a. 7x - 11y = 10
x + 2y = 5
y = ?
x = ?
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b. a - 9b = -4
a + 5b = 3
b = ?
a = ?

Answer 1

Explicación paso a paso:

$a) \\ 7x - 11y = 10 \\ x + 2y = 5 \\ x = 5 - 2y \\ 7(5 - 2y) - 11y = 10 \\ 35 - 14y - 11y = 10 \\ 35 - 25y = 10 \\ - 25y = 10 - 35 \\ - 25y = - 25 \\ 25y = 25 \\ y = \frac{25}{25} = 1$

$x = 5 - 2y = \\ 5 - 2 \times 1 = 5 - 2 = 3 \\ x = 3$

$a - 9b = - 4 \\ a + 5b = 3 \: \: \: ( \times - 1) \\ - a - 5b = - 3 \\ a - 9b = - 4 \\ - 14b = - 7 \\ 14b = 7 \\ b = \frac{7}{14}$

$a + 5b = 3 \\ a = 3 - 5b \\ = 3 - 5 \times \frac{7}{14} = 3 - \frac{35}{14} = \\ = \frac{42}{14} - \frac{35}{14} = \frac{7}{14} \\ a = \frac{7}{14}$

$\frac{7}{14} - 9 \times \frac{7}{14} = \frac{7}{14} - \frac{63}{14} = \frac{ - 56}{14} = - 4$

$\frac{7}{14} + 5 \times \frac{7}{14} = \frac{7}{14} + \frac{35}{14} = \frac{42}{14} = 3$

espero te sirva