# 1. Special Products

### What makes these products "special"?

The algebraic products on this page are used all the time in this chapter, and most of the math you will come across later. They are "special" because they are very common, and they're worth knowing.

If you can recognize these products easily, it makes your life easier later on.

## Special Products involving Squares

The following special products come from multiplying out the brackets. You'll need these often, so it's worth knowing them well.

a(x+y) =ax+ay(Distibutive Law)(

x+y)(x−y) =x^{2}−y^{2}(Difference of 2 squares)(

x+y)^{2}=x^{2}+ 2xy+y^{2}(Square of a sum)(

x−y)^{2}=x^{2}− 2xy+y^{2}(Square of a difference)

### Examples using the special products

**Example 1:** Multiply out 2*x*(*a* − 3)

**Example 2:** Multiply `(7s + 2t)(7s − 2t)`

**Example 3:** Multiply (12* *+ 5*ab*)(12 − 5*ab*)

**Example 4:** Expand (5*a* + 2*b*)^{2}

**Example 5: **Expand (*q* − 6)^{2}

**Example 6:** Expand (8*x* −* y*)(3*x* + 4*y*)

**Example 7:** Expand (*x* + 2 + 3*y*)^{2}

## Special Products involving Cubes

The following products are just the result of multiplying out the brackets.

(

x+y)^{3}=x^{3}+ 3x^{2}y+ 3xy^{2}+y^{3}(Cube of a sum)(

x−y)^{3}=x^{3}− 3x^{2}y+ 3xy^{2 }−y^{3}(Cube of a difference)(

x+y)(x^{2}−xy+y^{2}) =x^{3}+y^{3 }(Sum of 2 cubes)(

x−y)(x^{2}+xy+y^{2}) =x^{3 }−y^{3 }(Difference of 2 cubes)

These are also worth knowing well enough so you recognize the form, and the differences between each of them. (Why? Because it's easier than multiplying out the brackets and it helps us solve more complex algebra problems later.)

**Example: **Expand `(2s + 3)^3`

### Exercises

Expand:

(1) (*s *+ 2*t*)(*s *− 2*t*)

(2) (*i*_{1} + 3)^{2}

(3) (3*x *+ 10*y*)^{2}

(4) (3*p *− 4*q*)^{2}

Didn't find what you are looking for on this page? Try **search**:

### Online Algebra Solver

This algebra solver can solve a wide range of math problems. (Please be patient while it loads.)

Go to: Online algebra solver

### Ready for a break?

Play a math game.

(Well, not really a math game, but each game was made using math...)

### The IntMath Newsletter

Sign up for the free **IntMath Newsletter**. Get math study tips, information, news and updates each fortnight. Join thousands of satisfied students, teachers and parents!

### Share IntMath!

### Algebra Lessons on DVD

Easy to understand algebra lessons on DVD. See samples before you commit.

More info: Algebra videos