# wrong

15. ### Am I wrong?

Can some one please check my answer for question 7, I have a quiz tomorrow and I want to make sure I understand!!
16. ### Finding a counterexample to wrong derivatives

Hello Forum, I find this problem to be extremely difficult. Any help is appreacited! Each of the following "derivatives" has been done incorrectly. In each case below, find a counterexample, that shows why the reasoning is incorrect. Then correct the mistakes by finding the actual derivatives...
17. ### What did I do wrong on this implicit differentiation problem

Im supposed to find the slope of the tangent line at the point (3,2) for the function (4x^2+2y^2)^2-4x^2y=1864 So here's what I did 2(4x^2+2y^2)(8x+4yy')-4(2xy+x^2y')=0 (8x^2+4y^2)(8x+4yy')-8xy-4x^2y'=0 64x^3+32x^2yy'+32y^2x+16y^3y'-8xy-4x^2y'=0 y'(32x^y+16y^3-4x^2)=-64x^3-32y^2x+8xy...
18. ### Why is this trollmath wrong?

Hi forum, I saw this trollmath on youtube. i dont claim its correct, but i cant understand where the mistake is. help :) Consider a geometric series as follows: S = 2 + 4+ 8 + 16 + ...... [1] 2S = 4 + 8+ 16 + ...... [2] [2]-[1] S = 2 Clearly the last line is false, but where...
19. ### Limit problem (what's going wrong?)

{\lim _{x \to - \infty }}{\frac{4x}{\sqrt{x^{2}+4x}+x}}} This gives - \infty, which is correct. Dividing both the numerator and the denominator by x, we have {\lim _{x \to - \infty }}{\frac{4}{\sqrt{1+\frac{4}{x}}+1}}} now this gives me 2. What's wrong? P.S. I tested the values on a...
20. ### Limit problem (what's going wrong?)

{\lim _{x \to - \infty }}{\frac{4x}{\sqrt{x^{2}+4x}+x}}} This gives - \infty, which is correct. Dividing both the numerator and the denominator by x, we have {\lim _{x \to - \infty }}{\frac{4}{\sqrt{1+\frac{4}{x}}+1}}} now this gives me 2. What's wrong? P.S. I tested the values on a...