Algebra/Alegbra

Advertisement


Question
I really need to get my Algebra grade up and i need help with some of these problems here's one:
-12-d>-12+4d

Answer
Hi Hannah, I will be glad to help.

Solving inequalities is exactly like solving equations with 1 difference:
If you need to multiply or divide both sides of the inequality by a negative number, flip the inequality

Here's an example of the rule above
-2m < 16
Because you must divide both sides by -2, the inequality sign. Must be flipped, or changed from < to >
The solution here would be
m > -8

With your problem
-12 - d > -12 + 4d

Bring the variable to the left side by subtracting 4d from both sides to get
-12 - 5d > -12

Since we grouped the variables on the left side of the inequality, we want to group all the constants (numbers without variables) on the right.
To get rid of the -12 on the left, add 12 to both sides (since -12 + 12 = 0 )
-5d > 0
Notice adding 12 does not change the sign of the coefficient in front of d.  If you are unsure why it's -5d instead of 5d, please ask.

Divide both sides by -5 (since -5/-5 = 1). REMEMBER, since we are dividing by a negative, we must flip the inequality sign.

Answer
d < 0

If you are ever unsure if you have the correct answer, pick a value for the variable that makes the inequality true, here d=-1 would work, and plug it into the original inequality and see if it holds.  Here it does (-12 - (-1) = -11, -12 + 4(-1) = -16, and -11 is greater than -16)

I hope this helps

Anne

Algebra

All Answers


Answers by Expert:


Ask Experts

Volunteer


Anne Losch

Expertise

Solving equations, graphing, evaluatin equations, factoring, functions, systems of equations, rational equations, exponent, complex numbers, word problems, logarithms, polynomials, and all topics in an Algebra 1, Algebra 2, or College Algebra class

Experience

I have a teaching certificate, I have taught Algebra 1 & 2 as well as tutored those subjects and tutored in College Algebra.

Organizations
NEA, past NCTM, MAA, AMS, and ASCD

Education/Credentials
I hold a B.S. in mathematics and computer science from an accredited university and have gone back to school to get my teacher certificate. I hold more than enough credits for an education minor.

Past/Present Clients
I have worked at tutoring centers including Sylvan Learning and Huntington Learning Center. I have posted answers to mathematical questions on answers.com but would rather volunteer with AllExperts.

©2016 About.com. All rights reserved.