1. **State the problem:** We want to find the values of $a$ such that both roots of the quadratic equation $$(a-1)x^2 - 2x + 5 = 0$$ are greater than 2.
2. **Recall the quadratic formula:** For an equation $Ax^2 + Bx + C = 0$, roots are given by $$x = \frac{-B \pm \sqrt{B^2 - 4AC}}{2A}$$
3. **Identify coefficients:** Here, $A = a-1$, $B = -2$, and $C = 5$.
4. **Condition for roots to be real:** The discriminant must be non-negative:
$$\Delta = B^2 - 4AC = (-2)^2 - 4(a-1)(5) = 4 - 20(a-1) \geq 0$$
Simplify:
$$4 - 20a + 20 \geq 0 \Rightarrow 24 - 20a \geq 0 \Rightarrow 20a \leq 24 \Rightarrow a \leq \frac{24}{20} = 1.2$$
5. **Condition for roots to be greater than 2:** Both roots $x_1, x_2 > 2$.
6. **Use the fact that for quadratic $Ax^2 + Bx + C=0$ with $A \neq 0$, the parabola opens up if $A>0$ and down if $A<0$.**
7. **Evaluate the quadratic at $x=2$:**
$$f(2) = (a-1)(2)^2 - 2(2) + 5 = 4(a-1) - 4 + 5 = 4a - 4 - 4 + 5 = 4a - 3$$
8. **For both roots to be greater than 2, the parabola must be positive at $x=2$ if it opens upwards ($A>0$), so:**
$$f(2) > 0 \Rightarrow 4a - 3 > 0 \Rightarrow a > \frac{3}{4} = 0.75$$
9. **Also, since $A = a-1$, for parabola to open upwards:**
$$a - 1 > 0 \Rightarrow a > 1$$
10. **Combine conditions:**
- From discriminant: $a \leq 1.2$
- From $f(2) > 0$: $a > 0.75$
- From $A > 0$: $a > 1$
So the combined interval is:
$$1 < a \leq 1.2$$
11. **Check roots at boundary $a=1$: $A=0$ so not quadratic, discard.**
12. **Final answer:** Both roots are greater than 2 if and only if
$$\boxed{1 < a \leq 1.2}$$
Roots Greater 2 F86A10
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