50. Find the value of \( P+Q+R+S \), if (i) \( (P x-4) \) and \( (x+3) \) are the factors of \( 3 x^{2}+5 x-12 \). (ii) \( (x-5) \) and \( (Q x+3) \) are the factors of \( 2 x^{2}-7 x-15 \). (iii) \( (R x-3) \) and \( (S x-3) \) are the factors of \( 8 x^{2}-18 x \) +9 .

16. Determine whether \( f(x)=8 x-1 \) is one-to-one. If it is, find a formula for its inverse.

Factor completely. \[ 5 v^{2}-30 v+70 \]

16 Solve the system of equations using matrices. Use the Gaussian elimination method with back-substitution. \[ \begin{array}{r}x+y-z=-4 \\ 4 x-y+z=-1 \\ -x+5 y-4 z=1\end{array} \] The solution set is \( \{(\square, \square, \square)\} \). (Simplify your answers.)

\( \left.\begin{array}{l}1 \leftarrow \quad \begin{array}{l}\text { Write the augmented matrix for the system of linear equations. } \\ \begin{array}{rl}9 x+y+5 z & =5 \\ 7 x-3 y-z & =9 \\ x-6 y-5 z & =-4\end{array} \\ \text { Enter the augmented matrix. } \\ \square \square \square \square \square \square \square\end{array} \\ \square \square \square \square\end{array}\right] \)

Find the least common denominator of \( \frac{2}{x-6} \) and \( \frac{7}{x+6} \)