If 3x-9y=21 and 6x+3y=21, which of these could be a value of x or y
a.-5
b.-2
c.-1
d.4
e.5
f.9

This question is based on system of linear equation. Therefore,  the value of x and y for given equations is x = 4 and y = -1.

Given:

3x-9y=21                                (1)

6x+3y=21                                (2)

Now, we have to solve the both equation for x and y.

From equation (1), we get the value of x,

⇒ 3x-9y=21  

⇒ x - 3y = 7

⇒ x = 7 + 3y

Putting the value of x = 7 + 3y in equation (2).

We get,

⇒ 6x + 3y=21  

⇒ 6 ( 7 + 3y ) + 3 y = 21

⇒ 42 + 18y +3y =21

⇒ 42 +21 y = 21

⇒ y +2 = 1

⇒ y = -1

Putting the value of y= -1 in equation x = 7 + 3y.

We get,

⇒ x = 7 +3(-1)

⇒ x = 4

Therefore,  the value of x and y for given equations is x = 4 and y = -1.

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x=4, y=-1. (4, -1).

Step-by-step explanation:

3x-9y=21

6x+3y=21

simplify

x-3y=7

2x+y=7

x=3y+7

2(3y+7)+y=7

6y+14+y=7

14+7y=7

7y=7-14

7y=-7

y=-7/7=-1

x=3(-1)+7=-3+7=4

x=4, y=-1.

a

step-by-step explanation: