How many solutions does the system have?
21x + 6y = 42
7x + 2y = 14
choose one
1. exactly one solution.
2. no solutions.
3. infinitely many solutions.

For this case we have the following system of equations:

We multiply the second equation by -3:

Thus, we observe that the second equation is equivalent to the first, if we add both we get:

The equality is fulfilled. The lines are on top of each other.

Infinite solutions

Step-by-step explanation:

If you solve the equation system using a graph, then the solution is to intersect the line.

The graph has two parallel lines (no intersection). Therefore, this system of equations has no solutions.

Algebraic solution:

21x + 6x = 42    divide both sides by (-3)

-7x - 2x = -14

Add both equations by sides:

   7x + 2y = 14

+ -7x - 2y = -14

           0 = 0        TRUE

Therefore the system of equations has Infinitely many solutions.

-14

step-by-step explanation:

2x2 – 2(x+4)

=2x2-2（5+4）

=4-2×9

=4-18

=-14