You are here:

# Algebra/Algebra systems (12.7-3)

Advertisement

Question
Solve the following system via elimination:
y = x^2 + 2
-4x - y = 10

Thank you!

Answer
Take y and put it in the second equation.
This gives -4x - x² - 2 = 10.
Subtracting 10 from both sides gives -4x - x² - 2 = 10.
Rearranging terms and subtracting 10 from both sides gives -x² - 4x - 12 = 0.
Multiplying through by -1 gives x² + 4x + 12 = 0.

Since the square-root in the quadratic equation has b²-4ac,
and a=1, b=4, and c=12, this can be seen to give 16-48 = -32.

Have you dealt with the square-root of negative numbers?
If not, that is undefined.

If, on the other hand, you've dealt with them,
that gives a complex number as the answer for x.
Later in algebra, if you're not there yet, they define the square-root of -1.

As I said, if you haven't dealt with the square-root of negative numbers,
there is no solution.

Algebra

All Answers

Ask Experts

Volunteer

#### Scott A Wilson

##### Expertise

Any algebraic question you've got. That includes question that are linear, quadratic, exponential, etc.

##### Experience

I have solved story problems, linear equations, parabolic equations. I have also solved some 3rd order equations and equations with multiple variables.

Publications
Documents at Boeing in assistance on the manufacturiing floor.

Education/Credentials
MS at math OSU in mathematics at OSU, 1986. BS at OSU in mathematical sciences (math, statistics, computer science), 1984.

Awards and Honors
Both my BS and MS degrees were given with honors.

Past/Present Clients
Students in a wide variety of areas since the 80's; over 1,000 of them have been in algebra.

©2017 About.com. All rights reserved.

Browse Answers: