diff --git a/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Unit 2: Quadratic Equations 2.md b/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Unit 2: Quadratic Equations 2.md new file mode 100644 index 0000000..3184495 --- /dev/null +++ b/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Unit 2: Quadratic Equations 2.md @@ -0,0 +1,104 @@ +## Quadratic Equations 2 + +### Question 4 a) + +$`5x(x-1) + 5 = 7 + x(1-2x)`$ + +$`5x^2 - 5x = 2 + x - 2x^2`$ + +$`7x^2 - 6x - 2 = 0`$ + +$`x = \dfrac{6 \pm \sqrt{92}}{14} = \dfrac{3 \pm \sqrt{23}}{7}`$ + +### Question 4 b). + +$`\because \dfrac{1}{3}`$ and $`\dfrac{-2}{3}`$ are the roots of a quadratic equation, that must mean that $`(x-\dfrac{1}{3})(x+\dfrac{2}{3})`$ is a quadratic equation that +gives those roots. Here we make $`a=1`$, so its easy to find a quadratic in vertex from that gives these roots. + +Let the vertex form then be $`y=(x-d)^2+c`$, since $`a=1`$. + +We know $`d=\dfrac{r_1+r_2}{2}`$ because it is the x-coordinate of the vertex which is also the AOS. Therefore it is equal to $`\dfrac{\dfrac{1}{3} + \dfrac{-2}{3}}{2} = \dfrac{-1}{6}`$ + +Then, we know $`c=(d-\dfrac{1}{3})(d+\dfrac{2}{3})`$, since by plugging in the x-coordinate of the vertex, we get the y-coordinate of the vertex which is also the $`c`$ value. + +Therefore $`c=(\dfrac{-1}{6}-\dfrac{1}{3})(\dfrac{-1}{6} + \dfrac{2}{3}) = \dfrac{-1}{4}`$. + +Therefore our equation is simply $`y = (x+\dfrac{1}{6})^2 - \dfrac{1}{4}`$ + + +### Qustion 4 c) + +When $`h = 0`$, the ball hits ground, so: + +$`-3.2t^2 + 12.8 + 1 = 0`$ + +$`t = \dfrac{12.8 \pm \sqrt{151.04}}{6.4}`$ + +$`\because t \ge 0`$ + +$`\therefore t = \dfrac{12.8 \pm \sqrt{151.04}}{6.4}`$ + +$`\therefore t \approx 3.9`$ + +The ball will strike the ground at approximately $`3.9`$ seconds. + +### Question 5 a) + +$`128 = 96t - 16t^2`$ + +$`16t^2 - 96t + 128 = 0`$ + +$`t^2 - 6t + 8 = 0`$ + +$`(t-2)(t-4)`$, at seconds $`2`$ and $`4`$, the rocket reaches $`128m`$. + +### Question 5 b) + +Break even is when revenue = cost. + +$`\therefore R(d) = C(d)`$ + +$`-40d^2 + 200d = 300 - 40d`$ + +$`40d^2 - 240d + 300 = 0`$ + +$`2d^2 - 12d + 15 = 0`$ + +$`d = \dfrac{12 \pm \sqrt{24}}{4}`$ + +$`d = \dfrac{6 \pm \sqrt{6}}{2}`$ + +At $`d = 4.22474407`$ or $`1.775255135`$ is when you break even. + +### Question 5 c) + +Let the quation be $`y = a(x-d)^2 + c`$ + +Since we know that that $`(0, 0)`$ and $`(6, 0)`$ are the roots of this equation, the AOS is when $`x = 3`$ + +$`\therefore y = a(x-3)^2 + c`$. + +Since we know that $`(0, 0)`$ is a point on the parabola, we can susbsitute it into our equation. + +$`0 = 9a + c \quad (1)`$ + +Since we know that $`(4, 5)`$ is also a point on the parabola, we can susbsitute it int our equation as well. + +$`5 = a + c \quad (2)`$ + +```math +\begin{cases} +9a + c = 0 & \text{(1)} \\ +a + c = 5 & \text{(2)} \\ +\end{cases} +``` + +$`(2) - (1)`$ + +$`-8a = 5 \implies a = \dfrac{-5}{8} \quad (3)`$ + +Sub $`3`$ into $`(2)`$: + +$`5 = \dfrac{-5}{8} + c \implies c = \dfrac{45}{8}`$ + +$`\therefore`$ Our equation is $`y = \dfrac{-5}{8}(x-3)^2 + \dfrac{45}{8}`$ \ No newline at end of file