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Course: Algebra 1 (FL B.E.S.T.) > Unit 9
Lesson 6: Multiplying binomials by polynomialsMultiplying binomials by polynomials review
A review of how to multiply binomials like 1 + x by polynomials with more than two terms like x^2 - 5x - 6
We already know how to multiply binomials like
Example
Expand and simplify.
Apply the distributive property.
Apply the distributive property again.
Notice the pattern. We multiplied each term in the binomial by each term in the trinomial.
Simplify.
Want to learn more about multiplying binomials and polynomials? Check out this video.
Want more practice? Check out this exercise.
Want to join the conversation?
How do you simplify an equation(12 votes)
You just need to combine like terms. Example- t to the fourth plus t to the fourth; 2w squared plus w squared. I hope this helps and God bless!(47 votes)
What would be considered the fastest method of multiplying long polynomials?(6 votes)
Great question! Yes there is a shortcut, which efficiently combines all the terms for each power of x.
If only one variable, say x, appears in the two polynomials to be multiplied together, then you can use a technique similar to the Vedic multiplication arithmetic technique called vertical and crosswise (which you can look up online to get the idea). Write the terms of each polynomial in order of descending powers of x. For any missing exponents on x, use a coefficient of zero.
Example: multiply (6x^4 + 3x^3 - 5x + 7) by (2x^3 - 4x^2 - x + 8).
Write
(6x^4 + 3x^3 + 0x^2 - 5x + 7)
(0x^4 + 2x^3 - 4x^2 - x + 8).
These two polynomials are now each written with five coefficients.
The idea is to multiply the first coefficient by the first coefficient, then cross multiply the first two coefficients by the first two coefficients, then the first three by the first three, then the first four by the first four, then the first five by the first five, then the last four by the last four, then the last three by the last three, then the last two by the last two, then finally the last one by the last one.
There are no terms of degree 9 or higher.
Coefficient of x^8 is 6(0) = 0.
Coefficient of x^7 is 6(2) + 3(0) = 12.
Coefficient of x^6 is 6(-4) + 3(2) + 0(0) = -18.
Coefficient of x^5 is 6(-1) + 3(-4) + 0(2) + (-5)(0) = -18.
Coefficient of x^4 is 6(8) + 3(-1) + 0(-4) + (-5)(2) + 7(0) = 35.
Coefficient of x^3 is 3(8) + 0(-1) + (-5)(-4) + 7(2) = 58.
Coefficient of x^2 is 0(8) + (-5)(-1) + 7(-4) = -23.
Coefficient of x is -5(8) + 7(-1) = -47.
Constant term (coefficient on x^0) is 7(8) = 56.
The answer is
12x^7 - 18x^6 - 18x^5 + 35x^4 + 58x^3 - 23x^2 - 47x + 56.
Have a blessed, wonderful day!(56 votes)
So, you can apply the distributive property to one of these equations, or you can use the graph/colored boxes thing? Which way is more efficient?(8 votes)
There is FOIL, double distribution, and box method as 3 ways of doing the exact same thing, they all give the same 4 terms with the middle terms usually combined. FOIL is probably less efficient because it is limited to multiplying two binomials. The box method may require more writing, but might make more sense in exactly what is going on. Double distribution and box method can easily be expanded to larger polynomials in the future. Efficient may be in the eye of the beholder, so find which one works best for you. Many teachers will require you to learn all so that you can make an educated decision which is best, and if you do it enough and have a pretty good math brain, you will be able to do it in your head.(16 votes)
in the vid they never clearly said which goes first they just said its the only one cubed and do I do y squared first or y alone first(6 votes)
Generally, you should write your answer in standard form. This would have the term with y^2 first, then y, then the constant. However, it is usually not required unless the instructions specify your answer must be in standard form.(14 votes)
is this apart of the algebra 2 course(5 votes)
I would say this is something you learn in Algebra 1. This seems more like a review in Algebra 2.(12 votes)
What do you think is the best way to multiply and simplify a problem?(3 votes)
In my opinion, the area model is easier because I can see out all the terms and not get things mixed up. I tend to get numbers mixed up and write things wrong when I do the distributive property. However, it is your preference in the end!(14 votes)
Am I ever going to need this type of math in the real world?(7 votes)- I mean, you'll need it for the SAT or the ACT - the math in those is primarily Algebra 2, and stuff like this, but as far as the real world, it depends on your job... but we have computer software to do this stuff nowdays :)(5 votes)
- Most Confusing thing ever!!(8 votes)
- when you are multiplying without a coefficient how do you deal with the exponent.(3 votes)
- Please give an example to clarify. Everything has a coefficient. For example: x = 1x. The coefficient =1.
So, I don't understand what you mean.(11 votes)
for those who are having trouble with the distributive method you should try the box method its layed out in a way that may end up being easier to understand. its hard to put that method on the the chat but i hope that info helps.(i would look it up if you don´t understand what i mean by box method)(6 votes)
The 'Box method' is a great way to build up foundation for the distributive method. It interprets the steps visually making it overall easier to improve over time! It's always great to share methods with each other!(2 votes)
