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Which equation combines with the given equation to form a system of equations with the solution x = 3 and y = 9?
x + 2y = 21
A. 4x + 6y = 64
B. 2x + y = 36
C. 4x + y = 21
D. -3x + 4y = 33
E. 3x + 2y = 28

Respuesta :

Answer: c. 4x + y = 21

Step-by-step explanation:

The equation which is equal to the given expression is 4x + y = 21 i.e. option C.

What is expression ?

Expression is a finite combination of symbols that is well-formed according to rules that depend on the context.

We have,

x + 2y = 21     .....(i)

Solutions x = 3 and y = 9.

So,

Now putting the values of x and y in equation (i),

We get,

3 + 2 * 9 = 21

3 + 18 = 21

21 = 21

So,

Now check for every option,

Let,

A. 4x + 6y = 64

i.e.

Now putting the values of x and y in above equation,

We get,

4 * 3 + 6 * 9 ≠ 64

⇒ 48 ≠ 64

i.e. LHS is not equal RHS.

Now,

B. 2x + y = 36

i.e.

Now putting the values of x and y in above equation,

We get,

2 * 3 + 9 ≠ 36

⇒ 15 ≠ 36

i.e. LHS is not equal RHS.

Now,

C. 4x + y = 21

i.e.

Now putting the values of x and y in above equation,

We get,

4 * 3 + 9 = 21

⇒ 12 + 9 = 21

21 = 21

i.e. LHS is equal RHS, so it is equal to the given equation.

Hence, we can say that the equation which is equal to the given expression is 4x + y = 21 i.e. option C.

To know more about expression click here

https://brainly.com/question/953809

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