Question

3×-4y=15;×+y=-2 solve by elimination method and substitution method​

Answer 1

$\red {\boxed {\underline {( x , y ) = ( 1 , -3)}}}$

Step-by-step explanation:

3x - 4y = 15 ... ( 1 )

x + y = -2 ... ( 2 )

Multiply equation ( 2 ) with 4

( x + y = -2 ) × 4

= 4x + 4y = -8 ... ( 3 )

Add equation ( 1 ) and equation ( 3 )

3x - 4y = 15

+4x + 4y = -8

7x = 7

7x = 7

x = 7 / 7

x = 1

$\pink {\boxed {\underline {x = 1}}}$

Putting the value of x = 1 in equation ( 3 )

We get,

4x + 4y = -8 ... ( 3 )

4 ( 1 ) + 4y = -8

4 + 4y = -8

4y = -8 - 4

4y = -12

y = -12 / 4

y = -3

$\pink {\boxed {\underline {y = -3}}}$

$\red {\boxed {\underline {( x , y ) = ( 1 , -3)}}}$

___________________________

Let's check the value of x = 1 and y = -3 by putting them in equation ( 1 )

3x - 4y = 15 ... ( 1 )

3 ( 1 ) - 4 ( - 3 ) = 15

3 - -12 = 15

3 + 12 = 15

15 = 15

$\red {\boxed {\underline {( x , y ) = ( 1 , -3)}}}$