1. **State the problem:** Find all values of $m$ such that the inequalities hold for every real number $x$:
1. $m x (x - 2) < m^2 x^2 + 2$
2. $2x(2x + 1) - 1 < m x (m x + 1)$
2. **Analyze the first inequality:**
Rewrite the inequality:
$$m x (x - 2) < m^2 x^2 + 2$$
Expand the left side:
$$m x^2 - 2 m x < m^2 x^2 + 2$$
Bring all terms to one side:
$$m x^2 - 2 m x - m^2 x^2 < 2$$
Group $x^2$ terms:
$$(m - m^2) x^2 - 2 m x < 2$$
Define $A = m - m^2 = m(1 - m)$, so:
$$A x^2 - 2 m x < 2$$
Rewrite as:
$$A x^2 - 2 m x - 2 < 0$$
For the inequality to hold for all $x$, the quadratic function
$$f(x) = A x^2 - 2 m x - 2$$
must be strictly less than zero for all real $x$.
3. **Condition for $f(x) < 0$ for all $x$:**
- If $A > 0$, the parabola opens upward, so $f(x)$ will be negative only between roots, not for all $x$.
- If $A < 0$, the parabola opens downward, and $f(x)$ is less than zero outside the roots.
- To have $f(x) < 0$ for all $x$, the quadratic must have no real roots and open downward, so:
1. $A < 0$
2. Discriminant $D < 0$
4. **Calculate discriminant $D$ of $f(x)$:**
$$D = (-2 m)^2 - 4 imes A imes (-2) = 4 m^2 + 8 A = 4 m^2 + 8 m (1 - m) = 4 m^2 + 8 m - 8 m^2 = -4 m^2 + 8 m$$
5. **Apply conditions:**
- $A = m (1 - m) < 0$ implies $m (1 - m) < 0$.
This inequality holds when $m$ is between 0 and 1:
$$0 < m < 1$$
- $D < 0$:
$$-4 m^2 + 8 m < 0 \\ 8 m - 4 m^2 < 0 \\ 4 m (2 - m) < 0$$
Since $4 > 0$, the inequality reduces to:
$$m (2 - m) < 0$$
This holds when $m < 0$ or $m > 2$.
6. **Combine both conditions:**
- From $A < 0$: $0 < m < 1$
- From $D < 0$: $m < 0$ or $m > 2$
There is no overlap, so no $m$ satisfies both simultaneously.
Therefore, no $m$ makes the inequality true for all $x$ if $A
eq 0$.
7. **Check the case $A = 0$:**
$$m (1 - m) = 0 \\ m = 0 ext{ or } m = 1$$
- For $m=0$:
$$0 < 0 + 2$$
Inequality becomes:
$$0 < 2$$
True for all $x$.
- For $m=1$:
$$1 imes x (x - 2) < 1^2 x^2 + 2 \\ x^2 - 2 x < x^2 + 2 \\ -2 x < 2 \\ x > -1$$
This is not true for all $x$ (fails for $x o - ext{large}$).
8. **Conclusion for first inequality:**
The inequality holds for all $x$ only if:
$$m = 0$$
9. **Analyze the second inequality:**
$$2 x (2 x + 1) - 1 < m x (m x + 1)$$
Expand both sides:
Left:
$$4 x^2 + 2 x - 1$$
Right:
$$m^2 x^2 + m x$$
Inequality:
$$4 x^2 + 2 x - 1 < m^2 x^2 + m x$$
Bring all terms to one side:
$$4 x^2 + 2 x - 1 - m^2 x^2 - m x < 0$$
Group terms:
$$(4 - m^2) x^2 + (2 - m) x - 1 < 0$$
10. **Define:**
$$g(x) = (4 - m^2) x^2 + (2 - m) x - 1$$
We want $g(x) < 0$ for all real $x$.
11. **Conditions for $g(x) < 0$ for all $x$:**
- Parabola opens downward: coefficient of $x^2$ negative:
$$4 - m^2 < 0 \\ m^2 > 4 \\ m < -2 ext{ or } m > 2$$
- Discriminant $D_g < 0$:
$$D_g = (2 - m)^2 - 4 (4 - m^2)(-1)$$
$$= (2 - m)^2 + 4 (4 - m^2)$$
Expand:
$$(2 - m)^2 = m^2 - 4 m + 4$$
So:
$$D_g = m^2 - 4 m + 4 + 16 - 4 m^2 = -3 m^2 - 4 m + 20$$
12. **Solve $D_g < 0$:**
$$-3 m^2 - 4 m + 20 < 0 \\ 3 m^2 + 4 m - 20 > 0$$
Find roots of $3 m^2 + 4 m - 20 = 0$:
$$m = \frac{-4 \pm \sqrt{16 + 240}}{6} = \frac{-4 \pm 16}{6}$$
Roots:
$$m_1 = \frac{-4 - 16}{6} = -\frac{20}{6} = -\frac{10}{3} \approx -3.33$$
$$m_2 = \frac{-4 + 16}{6} = \frac{12}{6} = 2$$
Since leading coefficient is positive, inequality $3 m^2 + 4 m - 20 > 0$ holds for:
$$m < -\frac{10}{3} \text{ or } m > 2$$
13. **Combine conditions for $g(x) < 0$ for all $x$:**
- $m < -2$ or $m > 2$
- $m < -\frac{10}{3}$ or $m > 2$
Intersection:
- For $m < -2$, must also have $m < -\frac{10}{3} \approx -3.33$, so $m < -3.33$
- For $m > 2$, both conditions hold.
14. **Final solution for second inequality:**
$$m < -\frac{10}{3} \text{ or } m > 2$$
15. **Summary:**
- For inequality 1 to hold for all $x$: $$m = 0$$
- For inequality 2 to hold for all $x$: $$m < -\frac{10}{3} \text{ or } m > 2$$
**Answer:**
$$\boxed{\text{Inequality 1: } m=0; \quad \text{Inequality 2: } m < -\frac{10}{3} \text{ or } m > 2}$$
Inequalities M Values
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