diff --git a/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Quadratic Equations.md b/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Quadratic Equations.md index 05db896..773ad85 100644 --- a/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Quadratic Equations.md +++ b/Grade 10/Math/MPM2DZ/Math Oral Presentation Questions/Quadratic Equations.md @@ -1,4 +1,272 @@ ### Question 1 a) -The zeroes of a quadratic equation are the solutiosn of $`x`$ when $`ax^2+bx+c = 0`$. The roots of the quadratic equation is when $`(x + r_1)(x + r_2) = 0`$, more -commonly described by the formula $`\dfrac{-b \pm \sqrt{b^2-4ac}}{2a}`$. Therefore the roots of a quadratic equation are also the zeroes of the quadratic equation. \ No newline at end of file +The zeroes of a quadratic equation are the solutions of $`x`$ when $`ax^2+bx+c = 0`$. The roots of the quadratic equation is when $`(x + r_1)(x + r_2) = 0`$, more +commonly described by the formula $`\dfrac{-b \pm \sqrt{b^2-4ac}}{2a}`$. Therefore the roots of a quadratic equation are also the zeroes of the quadratic equation. + +### Question 1 b) + +$`D = b^2 - 4ac`$ + +If $`D=0`$, there is one zero. + +$`\therefore n^2 - 4(1)(4) = 0`$ + +$`n^2 - 16 = 0`$ + +$`(n+4)(n-4) = 0`$ + +$`n = \pm 4`$ + +### Question 1 c) + +Let $`h`$ be the height and $`b`$ be the base. $`h = 2b + 4`$. + +$`\therefore (2b+4)(b) = 168(2)`$ + +$`4b^2 + 8b = 168(2)`$ + +$`b^2 + 2b = 84 = 0`$ + +$`b = \dfrac{-2 \pm \sqrt{4+4(84)}`$ + +$`b = \dfrac{-2 \pmm \sqrt{340}}{2}`$ + +$`b = -1 + \sqrt{85}`$ + +### Question 2 a) + +If the quadratic is in $`ax^2 + bx + c`$, the AOS (axis of symmetry) is at $`\dfrac{-b}{2a}`$. And you can plug that value into the quadratic equation to get your optimal value, +which is: + +$`= a(\dfrac{-b}{2a})^2 + b(\dfrac{-b}{2a}) + c`$ + +$`= \dfrac{b^2}{4a} + \dfrac{-b^2}{2a} + c`$ + +$`= \dfrac{-b^2}{4a} + c`$ + +### Question 2 b) + +$`2x^2 + 5x - 1 = 0`$ + +$`2(x^2 + \dfrac{5}{2}x + (\dfrac{5}{4})^2 - (\dfrac{5}{4})^2) - 1 = 0`$ + +$`2(x+\dfrac{5}{4})^2 - \dfrac{25}{8} - 1 = 0`$ + +$`2(x+ \dfrac{5}{4})^2 - \dfrac{33}{8} = 0`$ + +$`(x+ \dfrac{5}{4})^2 = \dfrac{33}{16}`$ + +$`x = \pm \sqrt{\dfrac{33}{16}} - \dfrac{5}{4}`$ + +$`x = \dfrac{\pm \sqrt{33}}{4} - \dfrac{5}{4}`$ + +$`x = \dfrac{\sqrt{33}-5}{4}`$ or $`\dfrac{-\sqrt{33} - 5}{4}`$ + +### Question 2 c) + +Let $`w`$ be the width between the path and flowerbed, $`x`$ be the length of the whole rectangle and $`y`$ be the whole rectangle (flowerbed + path). + +$`x = 9+2w`$ + +$`y = 6+2w`$ + +$`(6+2w)(9+2w) - (6)(9 = (6)(9)`$ + +$`54 + 12w + 18w + 4w^2 = 2(54)`$ + +$`4w^2 + 30w = 54`$ + +$`2w^2 + 15w - 27 = 0`$ + +$`2 \quad \quad -3`$ + +$`1 \quad \quad 9`$ + +$`(2w-3)(w+9) = 0`$ + +$`w = \dfrac{3}{2}, -9`$ + +$`\because w \gt 0`$ + +$`\therefore w = \dfrac{3}{2}`$ + +$`\therefore x = 9+3 = 12`$ + +$`\therefore y = 6+3 = 9`$ + +$`P = 2(x + y) \implies P = 2(12+9) \implies P = 42`$ + +$`\therefore`$ The perimeter is $`42m`$ + +### Question 3 a) + +Use discriminant, where $`D = b^2 - 4ac`$. + +```math +\begin{cases} + +\text{If } D \gt 0 & \text{Then there are 2 real distinct solutions} \\ + +\text{If } D = 0 & \text{Then there is 1 real solution} \\ + +\text{If } D \lt 0 &\text{Then there are no real solutions} \\ + +\end{cases} +``` + +### Question 3 b) + +$`y = 12x^2 - 5x - 2`$ + +$`3 \quad \quad -2`$ + +$`4 \quad \quad 1`$ + +$`y = (3x-2)(4x+1)`$ + +$`\therefore`$ The $`x`$-intercepts are at $`\dfrac{2}{3}, \dfrac{-1}{4}`$ + +### Question 3 c) + +When $`P(x) = 0`$, that means it is the break-even point for a value of $`x`$ (no profit, no loss). +$`2k^2 + 12k - 10 = 0 \implies k^2 -6k + 5 = 0`$ + +$`(k-5)(k-1) = 0`$ + +$`k = 5, 1`$ + +Either $`5000`$ or $`1000`$ rings must be produced so that there is no prodift and no less. + +AOS (axis of symmetry) = $`\dfrac{-b}{2a} = \dfrac{6}{2} = 3`$ + +$`\therefore 3000`$ rings should be made to achieve the optimal value. + +Maximum profit $`= -2(3)^2 + 12(3) - 10`$ + +$`= -18 + 30 - 10`$ + +$` = 8`$ + +$`\therefore 8000`$ dollars is the maximum profit. + +### Question 4 a) + +$`5x(x-1) + 5 = 7 + x(1-2x)`$ + +$`5x^2 - 5x = 2 + x - 2x^2`$ + +$`7x^2 - 6x - 2 = 0`$ + +$`x = \dfrac{6 \pm \sqrt{92}}{14}`$ + +$`x = \dfrac{3 \pm \sqrt{23}}{7}`$ + +### 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. + +After expanind we get: + +$`y = x^2 - \dfrac{2}{3}x - \dfrac{1}{3}x + \dfrac{2}{3}`$ + +$`y = x^2 - x + \dfrac{2}{3}`$ + +Now we complete the square. + +$`y = x^2 - x + (\dfrac{1}{2})^2 - (\dfrac{1}{2})^2 + \dfrac{2}{3}`$ + +$`y = (x-\dfrac{1}{2})^2 - \dfrac{1}{4} + \dfrac{2}{3}`$ + +$`y = (x-\dfrac{1}{2})^2 + \dfrac{5}{12}`$ + +### Qustion 4 c) + +When $`h = 0`$, the ball hits ground, so: + +$`-3.2t^2 + 12.8 + 1 = 0`$ + +$`t = \dfrac{-12.8 \pm \sqrt{12.8^2 - 4(3.2)}}{-6.4}`$ + +$`t = \dfrac{12.8 \pm \sqrt{151.04}}{6.4}`$ + +$`\because t \ge 0`$ + +$`\therefore t = \dfrac{12.8 \pm sqrt{151.04}}{6.4}`$ + +$`\therefore t \approx 3.9`$ + +The ball will strike the ground at approximately $`3.9`$ seconds. + +### Question 5 a) + +$`128 = 96t - 16t^2`$ + +$`16t^2 - 96t + 128 = 0`$ + +$`t^2 - 6t + 8 = 0`$ + +$`1 \quad \quad -2`$ + +$`1 \quad \quad -4`$ + + +$`(t-2)(t-4)`$, at seconds $`2`$ and $`4`$, the rocket reaches $`128m`$. + +### Question 5 b) + +Break even is when revenue = cost. + +$`\therefore R(d) = C(d)`$ + +$`-40d^2 + 200d = 300 - 40d`$ + +$`40d^2 - 240d + 300 = 0`$ + +$`4d^2 - 24d + 30 = 0`$ + +$`2d^2 - 12d + 15 = 0`$ + +$`d = \dfrac{12 \pm \sqrt{24}}{4}`$ + +$`d = \dfrac{6 \pm \sqrt{6}}{2}`$ + +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 $`y = \dfrac{-5}{8}(x-3)^2 + \dfrac{45}{8}`$