Question

3x-5y=4 and 9x=2y+7 by substitution method​

Answer 1

Answer:

Given,

3x-5y=4

9x=2y+7

x= 2y+7 / 9

now,

3x-5y=4

3(2y+7 /9) -5y = 4

2y+7 / 3 -5y = 4

2y+7-15y / 3 = 4

2y+7-15y = 12

-13y+7 = 12

-13y = 5

y = -5/13

substitute y value in 3x-5y=4

3x- 5 ( -5/13) = 4

3x -25/13= 4

3x = 4 + 25/13

3x = 52+25 / 13

3x = 77 / 13

x = 77/39

Answer 2

Answer:

$x =\frac{9}{13}, y=-\frac{5}{13}$

Step-by-step explanation:

The equations are 3x - 5y = 4 and  9x = 2y + 7

from the second equation we get

$9x=2y+7\\\\\implies x=\frac{2y+7}{9}\\\\ Putting the expression of x from the second equation into the first equation. \\\\3(\frac{2y+7}{9} )-5y=4\\\\\implies\frac{2y+7}{3}-\frac{15y}{3}=4\\\\\implies\frac{7-13y}{3}=4\\\\\implies7-13y=12\\\\\implies-13y=5\\\\\implies y=-\frac{5}{13}$

Putting the value of y into the expression of x we get

$\therefore x =\frac{-2(\frac{5}{13})+7}{9}=\frac{7-\frac{10}{13}}{9} = \frac{\frac{91-10}{13} }{9}= \frac{\frac{81}{13} }{9}= \frac{9}{13}$