| AR.4D |
| Eq Edit |
| 12B | \( (2x - 3)(2x^2 + 5) \) | AR.4D | Eq Edit |
Instructional & Grading Notes
Page 1 of 2 • Teacher Answer Key
Worked Solutions & Factoring Guide Page 2 of 2
Polynomial Operations (Addition, Subtraction, Multiplication)
1A: \( (x^2 + 13) + (6x) = x^2 + 6x + 13 \)
3A: \( (4x - 60) - (3x^2 - 5x + 40) = 4x - 60 - 3x^2 + 5x - 40 = -3x^2 + 9x - 100 \)
4A: \( (5x - 6)(x^2 + 7) = 5x(x^2 + 7) - 6(x^2 + 7) = 5x^3 + 35x - 6x^2 - 42 = 5x^3 - 6x^2 + 35x - 42 \)
1B: \( (2x^2 - 8) + (5x + 3) = 2x^2 + 5x - 5 \)
3B: \( (5x - 45) - (x^2 - 2x + 35) = 5x - 45 - x^2 + 2x - 35 = -x^2 + 7x - 80 \)
4B: \( (4x - 7)(x^2 + 5) = 4x(x^2 + 5) - 7(x^2 + 5) = 4x^3 + 20x - 7x^2 - 35 = 4x^3 - 7x^2 + 20x - 35 \)
Geometric Models & Polynomial Division
5A: \( S(x) = 2(28.26x^2) + 18.84x^2 = 56.52x^2 + 18.84x^2 = 75.36x^2 \)
6A: Factor numerator: \( 2x^2 + 7x - 15 = (2x - 3)(x + 5) \). Divide by \( (2x - 3) \implies x + 5 \)
7A: Divide \( \frac{6x^3 + 19x^2 - 2x - 5}{2x + 1} = 3x^2 + 8x - 5 \) (Choice D)
8A: \( V = x(x + 3)(x + 5) = x(x^2 + 8x + 15) = x^3 + 8x^2 + 15x \)
5B: \( S(x) = 2(3.14x^2) + 6.28x^2 = 6.28x^2 + 6.28x^2 = 12.56x^2 \)
6B: Factor numerator: \( 3x^2 - 11x - 4 = (3x + 1)(x - 4) \). Divide by \( (3x + 1) \implies x - 4 \)
7B: Divide \( \frac{6x^3 + 17x^2 + 2x - 15}{2x + 3} = 3x^2 + 4x - 5 \) (Choice A)
8B: \( V = x(x + 1)(x + 6) = x(x^2 + 7x + 6) = x^3 + 7x^2 + 6x \)
Factoring Strategies (Trinomials, GCF, and Grouping)
Q9 (Trinomials \( a = 1 \)): Find factors of \( c \) adding to \( b \).
• 9A: \( x^2 - 11x + 24 \implies (-3)(-8) = 24 \text{ and } (-3) + (-8) = -11 \implies \mathbf{(x - 3)(x - 8)} \)
• 9B: \( x^2 - 9x + 20 \implies (-4)(-5) = 20 \text{ and } (-4) + (-5) = -9 \implies \mathbf{(x - 4)(x - 5)} \)
Q10 (Trinomials \( a > 1 \)): Split middle term or box method.
• 10A: \( 2x^2 + 13x + 15 \implies ac = 30 \); factors \( 10, 3 \implies 2x^2 + 10x + 3x + 15 = 2x(x + 5) + 3(x + 5) = \mathbf{(2x + 3)(x + 5)} \)
• 10B: \( 3x^2 + 14x + 8 \implies ac = 24 \); factors \( 12, 2 \implies 3x^2 + 12x + 2x + 8 = 3x(x + 4) + 2(x + 4) = \mathbf{(3x + 2)(x + 4)} \)
Q11 (GCF + Trinomial): Pull out greatest common factor \( x \) first.
• 11A: \( 3x^3 - 14x^2 + 8x = x(3x^2 - 14x + 8) \); factors of \( 24 \) adding to \( -14 \) are \( -12, -2 \implies \mathbf{x(3x - 2)(x - 4)} \)
• 11B: \( 2x^3 - 11x^2 + 12x = x(2x^2 - 11x + 12) \); factors of \( 24 \) adding to \( -11 \) are \( -8, -3 \implies \mathbf{x(2x - 3)(x - 4)} \)
Q12 (Grouping 4 Terms): Group first two and last two terms.
• 12A: \( (6x^3 - 15x^2) + (8x - 20) = 3x^2(2x - 5) + 4(2x - 5) = \mathbf{(2x - 5)(3x^2 + 4)} \)
• 12B: \( (4x^3 - 6x^2) + (10x - 15) = 2x^2(2x - 3) + 5(2x - 3) = \mathbf{(2x - 3)(2x^2 + 5)} \)
Page 2 of 2 • Teacher Answer Key