What is the solution to the system of equations? ⎧⎩⎨⎪⎪x+3y−z=24x+2y+5z=13x+z=12 (−4, 1, −3) (3, 0, 3) (5, −2, −3) (−1, 2, 3)

(5, -2, -3)

We assume your equations are ...

These have solution (x, y, z) = (5, -2, -3).

_____

How we know

Trying the choices in the last equation eliminates the first and last. Trying the second choice in the first equation eliminates it, leaving the 3rd choice as the answer you're looking for.

We also know because we can ask a graphing calculator to solve the matrix equation (or row-reduce the augmented matrix).

Comment on this problem

The hardest part of this problem is figuring your intent. The equations are not well-separated, so we have a hard time telling what is a constant and what is a coefficient. It took a couple of guesses to sort it out. A little editing before posting would be helpful.

none of the above.

for one of the equations to be used in the process, there has to be a term in the equation since squared is .

since there is only a term in the first equation, we cannot derive a from completing the square.

solving with completing the square

i believe your answer is 99.7% of 7-year-old children are between 46.6 inches and 49.5 inches tall.