1. **Problem 2a:** Express $2x^2 - 8x + 5$ in the form $a(x + b)^2 + c$, where $a$, $b$, and $c$ are integers.
2. The formula to complete the square for a quadratic $ax^2 + bx + c$ is:
$$a\left(x + \frac{b}{2a}\right)^2 + \left(c - a\left(\frac{b}{2a}\right)^2\right)$$
3. For $2x^2 - 8x + 5$, identify $a=2$, $b=-8$, and $c=5$.
4. Calculate $\frac{b}{2a} = \frac{-8}{2 \times 2} = \frac{-8}{4} = -2$.
5. Write the expression as:
$$2\left(x - 2\right)^2 + \left(5 - 2 \times (-2)^2\right)$$
6. Calculate the constant term inside the parentheses:
$$5 - 2 \times 4 = 5 - 8 = -3$$
7. So the expression in completed square form is:
$$2(x - 2)^2 - 3$$
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1. **Problem 2b:** Write down the equation of the line of symmetry for the graph of $y = 2x^2 - 8x + 1$.
2. The line of symmetry for a parabola $y = ax^2 + bx + c$ is given by:
$$x = -\frac{b}{2a}$$
3. Here, $a=2$, $b=-8$, so:
$$x = -\frac{-8}{2 \times 2} = \frac{8}{4} = 2$$
4. Therefore, the line of symmetry is:
$$x = 2$$
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1. **Problem 3a:** Express $7 + 5x - x^2$ in the form $a - (x + b)^2$, where $a$ and $b$ are constants.
2. Rewrite the quadratic in standard form:
$$-x^2 + 5x + 7$$
3. Factor out $-1$ from the $x^2$ and $x$ terms:
$$-(x^2 - 5x) + 7$$
4. Complete the square inside the parentheses:
$$x^2 - 5x = x^2 - 5x + \cancel{\left(\frac{5}{2}\right)^2} - \cancel{\left(\frac{5}{2}\right)^2} = (x - \frac{5}{2})^2 - \left(\frac{5}{2}\right)^2$$
5. Substitute back:
$$-\left[(x - \frac{5}{2})^2 - \left(\frac{5}{2}\right)^2\right] + 7 = - (x - \frac{5}{2})^2 + \left(\frac{5}{2}\right)^2 + 7$$
6. Calculate constants:
$$\left(\frac{5}{2}\right)^2 = \frac{25}{4}$$
7. So:
$$- (x - \frac{5}{2})^2 + \frac{25}{4} + 7 = - (x - \frac{5}{2})^2 + \frac{25}{4} + \frac{28}{4} = - (x - \frac{5}{2})^2 + \frac{53}{4}$$
8. Express in the form $a - (x + b)^2$:
$$a = \frac{53}{4}, \quad b = -\frac{5}{2}$$
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1. **Problem 3b:** Find the coordinates of the turning point of $y = 7 + 5x - x^2$ and state whether it is a maximum or minimum.
2. From the completed square form:
$$y = - (x - \frac{5}{2})^2 + \frac{53}{4}$$
3. The turning point is at $x = \frac{5}{2}$.
4. Substitute $x = \frac{5}{2}$ into $y$:
$$y = - (\frac{5}{2} - \frac{5}{2})^2 + \frac{53}{4} = \frac{53}{4}$$
5. Since the coefficient of the squared term is negative ($-1$), the parabola opens downward, so the turning point is a maximum.
6. Therefore, the turning point is:
$$\left(\frac{5}{2}, \frac{53}{4}\right)$$ which is a maximum point.
Quadratic Completion Bd0A76
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