These are four questions and four answers:
Question 1. Eliminate the parameter. x = 5t, y = t + 8
Answer: option B: y = (x / 5) + 8 ↔ x divided by 5 + 8
Explanation:
1) From x = 5t => t = x / 5
2) Substitute t in y = t + 8 => y = (x / 5) + 8
Which is the option B) y = the division of x by 5, added to 8.
Question 2. Eliminate the parameter.
There is an error in the question, because it says x = √x
If the righ question is x = √t , y = 3t + 7 , then the answer is the option A) y = 3x^2 + 7
Explanation:
1) Given: x = √t , y = 3t + 7
2) from x = √t => t = x^2
3) Substitute t = x^2 in y = 3t + 7
=> y = 3 x^2 + 7 ↔ option A) y = x^2 + 7
Question 3. Eliminate the parameter.
x = t^2 + 2, y = t^2 - 4
Answer: option A) y = x - 6
Explanation:
1) From x = t^2 + 2 => t^2 = x - 2
2) Substitute t^2 in y = t^2 - 4
=> y = x - 2 - 4
=> y = x - 6, since t^2 is ≥ 0, then x ≥ 0
=> option A) y = x - 6, x ≥ 1
Question 4. Eliminate the parameter.
x = 4 cos t, y = 4 sin t
Answer: x^2 + y^2 = 16
Explanation:
1) Square both sides of x = 4 cost
=> x^2 = (4 cos t)^2
x^2 = 16 (cos t)^2
2) Square both sides of y = 4 sin t
y^2 = 16 (sin t)^2
3) Add x^2 and y^2
x^2 + y^2 = 16(cos t)^2 + 16 (sin t)^2
=> x^2 + y^2 = 16 [ (cos t)^2 + (sin t)^2 ]
4) since (cos t)^2 + (sin t)^2 = 1
x^2 + y^2 = 16
