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 Sep 20 asked Why is $|(x-2)| < \delta \le 1$ true when proving $\lim_{x\to2}(3x^2-x)=10$? Sep 19 comment Proving $\lim_{x\to1}(x^2+3)=4$ Hm I'm not very sure how can $|x-1| < \delta$ lead to $|x+1|\le 3$. If you increase $|x-1|$ by $2$ to reach $|x+1|$, shouldn't it be $|x+1| \le 2$ rather than $3$? Sep 19 accepted Proving $\lim_{x\to1}(x^2+3)=4$ Sep 19 comment Why does $|x-1|^2+3|x-1| < \epsilon \implies |x-1|^2 < \frac{\epsilon}{2} \ \ \land \ \ 3|x-1| < \frac{\epsilon}{2}$? @Oleg567: What if $a = b = \epsilon/2$? Sep 19 asked Why does $|x-1|^2+3|x-1| < \epsilon \implies |x-1|^2 < \frac{\epsilon}{2} \ \ \land \ \ 3|x-1| < \frac{\epsilon}{2}$? Sep 19 asked Proving $\lim_{x\to1}(x^2+3)=4$ Sep 12 asked Determinant of a matrix with trigonometry functions. Sep 7 asked Determining what values in a system can cause infinite/unique/no solutions. Sep 7 comment For what values of $p$ and $b$ is the vector $(b,8,b+7)$ a solution of this system? Thanks, that's right (although $b$ yields $-5$). Sep 7 accepted For what values of $p$ and $b$ is the vector $(b,8,b+7)$ a solution of this system? Sep 7 comment For what values of $p$ and $b$ is the vector $(b,8,b+7)$ a solution of this system? @Adriano: Huh, it seems it should be $b = -5$. The exercise's answer seems to be wrong haha. Sep 7 revised For what values of $p$ and $b$ is the vector $(b,8,b+7)$ a solution of this system? added 1 character in body Sep 7 asked For what values of $p$ and $b$ is the vector $(b,8,b+7)$ a solution of this system? Sep 5 accepted Determining the values of $b$ in $Ax=b$ to have a consistent system. Sep 5 asked Determining the values of $b$ in $Ax=b$ to have a consistent system. Sep 1 accepted Is $A$ invertible if $ABAB^2 = I$? Sep 1 comment Is $A$ invertible if $ABAB^2 = I$? Only of the same size? Sep 1 asked Is $A$ invertible if $ABAB^2 = I$? Sep 1 asked Why does a matrix column being a multiple of another imply that the matrix is singular? Aug 27 awarded Popular Question