Factoring Techniques
When you're looking at polynomial expressions, grouping is a powerful strategy that works with 4 terms. The key is finding patterns that let you rewrite the expression more simply.
For example, with expressions like x3+2x2−3x−6, you can factor by grouping: x(x+2)−3(x+2)=(x+2)(x2−3). Notice how (x+2) appears in both parts, making it a common factor.
Difference of squares is another important pattern: 4x2−81=(2x+9)(2x−9). Remember: a2−b2=(a+b)(a−b). For perfect cubes, remember these formulas:
- a3+b3=(a+b)(a2−ab+b2)
- a3−b3=(a−b)(a2+ab+b2)
Pro Tip: When facing complex expressions, try factoring out the greatest common factor first, then look for patterns like difference of squares or perfect cubes.
Let's see factoring in action with a word problem. A landscape architect needs to design a marble planter holding 4 cubic feet of soil. If length = 6x height, width = 3x height, and sides are 1 foot thick, we can use factoring to find the dimensions: 18x3−18x2+4x−4=0. After factoring to (x−1)(18x2+4)=0, we get x=1, making the outer dimensions 1ft height, 3ft width, and 6ft length.