Solve (1,2) [(3x,-,y,=,1),(2x,+,3y,=,8)]

Find the linear approximation of the function $f(x)=\sqrt{4-x}$ at $a=0$
Use L(x) to approximate the numbers $\sqrt{3.9}$ and $\sqrt{3.99}$ Round to four decimal places

Suppose that the augmented matrix for a system of linear equations has been reduced by row operations to the given row echelon form. Solve the system.
${\displaystyle \left[\begin{array}{ccccc}1& 0& 6& 3& -4\\ 0& 1& 3& 7& 2\\ 0& 0& 1& 1& 4\end{array}\right]}$

Solve the linear system of equations.
$-5x-2y=1$
$2x-11y=-83$
$(x,y)=$

How to solve this linear pde for $y(x)$ (other functions are known and $\lambda$ is a constant):
$\frac{d}{dx}(g(x)y^{\prime }(x))={\lambda }^{2}g(x)y(x)$
Everything I know about this equation is that it is called the Sturmian equation. I did some research, but the theory, which is for a more general form of the equation, is too hard for me to understand.

2n +2 = 16

find an equation of the form $y=a{x}^2+bx+c$, whose graph passess through the points (2, 3), (-2, 7) and (1, -2). You must use a system of linear equations in three variables for this problem.

Determine whether the ordered pair is a solution to the given system of linear equations.
(1,2)
$\left\{\begin{array}{c}3x-y=1\\ 2x+3y=8\end{array}\right\}$