Mathematics » Introducing Polynomials » Multiplying Polynomials

Multiplying a Trinomial by a Binomial

Multiplying a Trinomial by a Binomial

We have multiplied monomials by monomials, monomials by polynomials, and binomials by binomials. Now we’re ready to multiply a trinomial by a binomial. Remember, the FOIL method will not work in this case, but we can use either the Distributive Property or the Vertical Method. We first look at an example using the Distributive Property.

Example

Multiply using the Distributive Property: \(\left(x+3\right)\left(2{x}^{2}-5x+8\right).\)

Solution

 Multiplying a Trinomial by a Binomial
Distribute.Multiplying a Trinomial by a Binomial
Multiply.\(2{x}^{3}-5{x}^{2}+8x+6{x}^{2}-15x+24\)
Combine like terms.\(2{x}^{3}+{x}^{2}-7x+24\)

Now let’s do this same multiplication using the Vertical Method.

Example

Multiply using the Vertical Method: \(\left(x+3\right)\left(2{x}^{2}-5x+8\right).\)

Solution

It is easier to put the polynomial with fewer terms on the bottom because we get fewer partial products this way.

 Multiplying a Trinomial by a Binomial
Multiply \(\left(2{x}^{2}-5x+8\right)\) by 3.Multiplying a Trinomial by a Binomial
Multiply \(\left(2{x}^{2}-5x+8\right)\) by \(x\).Multiplying a Trinomial by a Binomial
Add like terms.Multiplying a Trinomial by a Binomial

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