A curve is defined in parametric form by `x=2+t` and `y=3-2t^(2)` for `-1 <= t <= 0`.
Which diagram best represents this curve?
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A curve is defined in parametric form by `x=2+t` and `y=3-2t^(2)` for `-1 <= t <= 0`.
Which diagram best represents this curve?
`B`
`x=2+t\ \ =>\ \ t=x-2`
`text{Substitute into}\ \ y=3-2t^(2)`
`y=3-2(x-2)^2`
`text{Concave down parabola with maximum at (2, 3)}`
`=>B`
The variable point `(3t, 2t^2)` lies on a parabola.
Find the Cartesian equation for this parabola. (2 marks)
`y = (2x^2)/9`
`x = 3t \ => \ t = x/3`
`text(Substitute)\ \ t = x/3\ \ text(into)\ \ y = 2t^2`
`y = 2 xx (x/3)^2`
`y = (2x^2)/9`
A curve has parametric equations `x = t/2, y = 3t^2`.
Find the Cartesian equation for this curve. (2 marks)
`y = 12x^2`
`x = t/2 \ => \ t = 2x`
`text(Substitute)\ \ t = 2x\ \ text(into)\ \ y = 3t^2`
`y = 3(2x)^2`
`y = 12x^2`
`x = 4t - 7`
`y = 2t^2 + t` (2 marks)
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i. `x = 4t – 7 \ \ => \ \ t = (x + 7)/4`
`y` | `= 2t^2 + t` |
`y` | `= 2((x + 7)/4)^2 + ((x + 7)/4)` |
`16y` | `= 2(x + 7)^2 + 4(x + 7)` |
`16y` | `= 2x^2 + 28x + 98 + 4x + 28` |
`16y` | `= 2x^2 + 32x + 126` |
`8y` | `= x^2 + 16x + 63` |
`y` | `= 1/8(x + 7)(x + 9)` |
`=>\ text(Equation is a concave up quadratic with)`
`text(zeros at)\ \ x = −9\ text(and)\ \ x = −7.`
ii. `text(Axis at)\ \ x = −8`
`:.\ y_text(min)` | `= 1/8(−1)(1)` |
`= −1/8` |
`text(Domain: all)\ x`
`text(Range:)\ −1/8 <= y < ∞`
Find the Cartesian equation for the curve with the parametric equations
`x = 3t`
`y = 2t^2`. (1 mark)
`y = 2/9 x^2`
`x = 3t\ …\ (1)`
`y = 2t^2\ …\ (2)`
`text(Substitute)\ \ t = x/3\ \ text{from (1) into (2)}:`
`y = 2(x/3)^2`
`y = 2/9 x^2`