Line Curve Intersection
1. **State the problem:**
Find the coordinates of the points A and B where the line $y=4x-3$ meets the curve $y=3+5x-2x^2$. Then find the area of triangle $POQ$ formed by the perpendicular bisector of $AB$ intersecting the coordinate axes.
2. **Find points A and B:**
Set the line equal to the curve:
$$4x - 3 = 3 + 5x - 2x^2$$
Bring all terms to one side:
$$0 = 3 + 5x - 2x^2 - (4x - 3)$$
Simplify:
$$0 = 3 + 5x - 2x^2 - 4x + 3 = 6 + x - 2x^2$$
Rearranged:
$$-2x^2 + x + 6 = 0$$
Multiply by $-1$ to simplify:
$$2x^2 - x - 6 = 0$$
3. **Solve the quadratic:**
Using the quadratic formula $x=\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ with $a=2$, $b=-1$, $c=-6$:
$$x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4 \times 2 \times (-6)}}{2 \times 2} = \frac{1 \pm \sqrt{1 + 48}}{4} = \frac{1 \pm \sqrt{49}}{4} = \frac{1 \pm 7}{4}$$
So:
$$x_1 = \frac{1 + 7}{4} = 2$$
$$x_2 = \frac{1 - 7}{4} = -\frac{3}{2}$$
4. **Find y-coordinates:**
Using the line $y=4x-3$:
For $x=2$:
$$y = 4(2) -3 = 8 -3 = 5$$
For $x=-\frac{3}{2}$:
$$y = 4 \times (-\frac{3}{2}) - 3 = -6 - 3 = -9$$
Thus,
$$A = (2, 5), \quad B = \Big(-\frac{3}{2}, -9\Big)$$
5. **Find midpoint M of AB:**
$$M_x = \frac{2 + (-\frac{3}{2})}{2} = \frac{2 - 1.5}{2} = \frac{0.5}{2} = 0.25$$
$$M_y = \frac{5 + (-9)}{2} = \frac{-4}{2} = -2$$
Midpoint $M = (0.25, -2)$.
6. **Find slope of AB:**
$$m_{AB} = \frac{5 - (-9)}{2 - (-\frac{3}{2})} = \frac{14}{2 + 1.5} = \frac{14}{3.5} = 4$$
7. **Slope of perpendicular bisector:**
$$m_{perp} = -\frac{1}{m_{AB}} = -\frac{1}{4}$$
8. **Equation of perpendicular bisector:**
Using point-slope form at $M(0.25, -2)$:
$$y - (-2) = -\frac{1}{4}(x - 0.25)$$
Simplify:
$$y + 2 = -\frac{1}{4}x + \frac{1}{16}$$
$$y = -\frac{1}{4}x + \frac{1}{16} - 2$$
$$y = -\frac{1}{4}x - \frac{31}{16}$$
9. **Find intercepts P and Q:**
- $P$ on $x$-axis: set $y=0$
$$0 = -\frac{1}{4}x - \frac{31}{16}$$
Multiply both sides by 16:
$$0 = -4x - 31$$
$$4x = -31$$
$$x = -\frac{31}{4} = -7.75$$
So $P = (-7.75, 0)$.
- $Q$ on $y$-axis: set $x=0$
$$y = -\frac{1}{4} \times 0 - \frac{31}{16} = -\frac{31}{16} = -1.9375$$
So $Q = (0, -1.9375)$.
10. **Calculate area of triangle POQ:**
With vertices $P(-7.75, 0)$, $O(0,0)$, $Q(0, -1.9375)$, the triangle is right-angled at $O$, area is:
$$\text{Area} = \frac{1}{2} \times |x_P| \times |y_Q| = \frac{1}{2} \times 7.75 \times 1.9375 = \frac{1}{2} \times 15.00390625 = 7.501953125$$
Rounded:
$$\approx 7.50$$
**Final answers:**
(a) $A = (2, 5)$, $B = (-\frac{3}{2}, -9)$
(b) Area of triangle $POQ$ is approximately $7.50$ units squared.