Step-by-Step Questions, Tutorials, and Solutions
Factoring by grouping is a technique used when a polynomial has four or more terms and no common factor exists for all of them. By breaking the expression into smaller groups, we can often find a common binomial factor.
Factor completely the polynomial: \[ 4x^2 + 4x + 3x + 3 \]
1. Group the first two terms and factor out $4x$:
\[ 4x^2 + 4x = 4x(x + 1) \]
2. Group the last two terms and factor out $3$:
\[ 3x + 3 = 3(x + 1) \]
3. Rewrite and factor out the common binomial $(x + 1)$:
\[ 4x(x + 1) + 3(x + 1) = (x + 1)(4x + 3) \]
Factor: \[ 2x^2 - 4x + 3xy - 6y \]
1. Group terms with $x$: \( 2x^2 - 4x = 2x(x - 2) \)
2. Group terms with $y$: \( 3xy - 6y = 3y(x - 2) \)
3. Combine: \[ 2x(x - 2) + 3y(x - 2) = (x - 2)(2x + 3y) \]
Factor completely: \[ 3x^2 + 4x + 1 \]
Since there are only three terms, we split the middle term $4x$ into $3x + x$ to enable grouping:
\[ 3x^2 + 3x + x + 1 \]Now group and factor:
\[ (3x^2 + 3x) + (x + 1) = 3x(x + 1) + 1(x + 1) \] \[ = (x + 1)(3x + 1) \]Use grouping to factor the following polynomials completely.
Practice A: \( x^2 + 3x - 2x - 6 \)
Graphical Check: The x-intercepts of the graph $y = x^2 + 3x - 2x - 6$ correspond to the roots $x = -3$ and $x = 2$.
Practice B: \( 4x^2 + x - 3 \)
Rewrite $x$ as $4x - 3x$:
\[ 4x^2 + 4x - 3x - 3 = 4x(x + 1) - 3(x + 1) = (x + 1)(4x - 3) \]Practice C: \( x^2y + 3x + x^2y^2 + 3xy \)
First, factor out the common $x$ from all terms:
\[ x(xy + 3 + xy^2 + 3y) \]Now group inside the parentheses:
\[ x[xy(1 + y) + 3(1 + y)] = x(1 + y)(xy + 3) \]Practice D: \( 3x^2 + 3xy - x + 2y - 2 \)
Rewrite $-x$ as $-3x + 2x$ to create six terms:
\[ 3x^2 + 3xy - 3x + 2x + 2y - 2 \]Group the first three and last three terms:
\[ 3x(x + y - 1) + 2(x + y - 1) = (x + y - 1)(3x + 2) \]