1. State the problem.
Problem: Multiply out and simplify the following expressions a) $x - 2(x + 2) - 2(x - 2)^2$ b) $x - 2(x + 2) - 2(x - 2)(x + 2)$ c) $(2a - 3)^2 - (2a - 3)(3a + 2)$ d) $(x/3 - 3/2)^2 - (x/3 - 3/2)(x/3 + 3/2)$.
2. Formula and rules.
Use the distributive law: $a(b+c)=ab+ac$.
Use the square of a binomial: $ (u - v)^2 = u^2 - 2uv + v^2$.
When subtracting an expression, distribute the negative sign to each term inside the parentheses.
3. Work and final answers.
3.a) Expand and simplify step by step.
$$(x-2)^2 = x^2 - 4x + 4$$
$$x - 2(x + 2) - 2(x - 2)^2 = x - 2x - 4 - 2(x^2 - 4x + 4)$$
$$= x - 2x - 4 - 2x^2 + 8x - 8$$
$$= -2x^2 + 7x - 12$$
Final answer for a): $-2x^2 + 7x - 12$.
3.b) Expand and simplify step by step.
$$(x - 2)(x + 2) = x^2 - 4$$
$$x - 2(x + 2) - 2(x - 2)(x + 2) = x - 2x - 4 - 2(x^2 - 4)$$
$$= x - 2x - 4 - 2x^2 + 8$$
$$= -2x^2 - x + 4$$
Final answer for b): $-2x^2 - x + 4$.
3.c) Expand squares and products and simplify.
$$(2a - 3)^2 = 4a^2 - 12a + 9$$
$$(2a - 3)(3a + 2) = 6a^2 - 5a - 6$$
$$(2a - 3)^2 - (2a - 3)(3a + 2) = 4a^2 - 12a + 9 - (6a^2 - 5a - 6)$$
$$= 4a^2 - 12a + 9 - 6a^2 + 5a + 6$$
$$= -2a^2 - 7a + 15$$
Final answer for c): $-2a^2 - 7a + 15$.
3.d) Factor a common term and simplify using cancellation.
$$ (x/3 - 3/2)^2 - (x/3 - 3/2)(x/3 + 3/2) = (x/3 - 3/2)\left((x/3 - 3/2) - (x/3 + 3/2)\right)$$
$$= (x/3 - 3/2)\left(\cancel{x/3} - \cancel{x/3} - 3/2 - 3/2\right)$$
$$= (x/3 - 3/2)(-3)$$
$$= -3\cdot \frac{x}{3} + \frac{9}{2}$$
$$= -\frac{3x}{3} + \frac{9}{2}$$
$$= -\frac{\cancel{3}x}{\cancel{3}} + \frac{9}{2}$$
$$= -x + \frac{9}{2}$$
Final answer for d): $-x + 9/2$.
Multiply Simplify 761E03
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