Question

PLEASE HELP

Which is the best first step when solving the following system of equations?
y=7x+3
y=9x
A.Multiply the first equation by –7.
B.Substitute 9x for y in the first equation.
C.Multiply the second equation by Negative 3.
D.Substitute 7x for y in the second equation.

Answer 1

B. Substitute 9x for y in the first equation

Explanation:

There are various ways of solving a system of linear equations:

- Graphing

- Substitution

- Elimination

Here, given that we have two equations that are equal to y in terms of x, we can use substitution and essentially either plug in the expression (7x + 3) in for y in the second equation or plug in the expression (9x) in for y in the first equation.

Look at the answer choices: only B matches, so it's the correct answer.

Answer 2

Explanation:

Step 1: Find the most reasonable step

Option A: It doesn't make sense because that will not help us solve the system of equation.

Option B: This option makes sense because you can then solve for x.

Option C: It doesn't make sense because that will not help us solve the system of equation.

Option D: It doesn't make sense because that will not help us solve the system of equation.

Answer: Option B