Factoring Equations
1. Solve each equation by factoring.
### a) $x^4 - 16x^2 + 75 = 2x^2 - 6$
1. Move all terms to one side:
$$x^4 - 16x^2 + 75 - 2x^2 + 6 = 0$$
2. Simplify:
$$x^4 - 18x^2 + 81 = 0$$
3. Recognize it as a quadratic in $x^2$:
Let $y = x^2$, then
$$y^2 - 18y + 81 = 0$$
4. Factor the quadratic:
$$(y - 9)^2 = 0$$
5. So $y = 9$, thus $x^2 = 9$
6. Solve for $x$:
$$x = \pm 3$$
### b) $2x^2 + 4x - 1 = x + 1$
1. Move all terms to one side:
$$2x^2 + 4x - 1 - x - 1 = 0$$
2. Simplify:
$$2x^2 + 3x - 2 = 0$$
3. Factor the quadratic:
$$(2x - 1)(x + 2) = 0$$
4. Set each factor to zero:
- $2x - 1 = 0 \Rightarrow x = \frac{1}{2}$
- $x + 2 = 0 \Rightarrow x = -2$
### c) $4x^3 - x^2 - 2x + 2 = 3x^3 - 2(x^2 - 1)$
1. Expand right side:
$$3x^3 - 2x^2 + 2$$
2. Move all terms to left side:
$$4x^3 - x^2 - 2x + 2 - 3x^3 + 2x^2 - 2 = 0$$
3. Simplify:
$$x^3 + x^2 - 2x = 0$$
4. Factor out $x$:
$$x(x^2 + x - 2) = 0$$
5. Factor quadratic:
$$x(x + 2)(x - 1) = 0$$
6. Solutions:
$$x = 0, x = -2, x = 1$$
### d) $-2x^2 + x - 6 = -x^3 + 2x - 8$
1. Move all terms to one side:
$$-2x^2 + x - 6 + x^3 - 2x + 8 = 0$$
2. Simplify:
$$x^3 - 2x^2 - x + 2 = 0$$
3. Try factoring by grouping:
$$x^3 - 2x^2 - x + 2 = (x^3 - 2x^2) - (x - 2)$$
4. Factor each group:
$$x^2(x - 2) - 1(x - 2)$$
5. Factor out $(x - 2)$:
$$(x - 2)(x^2 - 1) = 0$$
6. Factor difference of squares:
$$(x - 2)(x - 1)(x + 1) = 0$$
7. Solutions:
$$x = 2, x = 1, x = -1$$
Final answers:
- a) $x = \pm 3$
- b) $x = \frac{1}{2}, -2$
- c) $x = 0, -2, 1$
- d) $x = 2, 1, -1$