Solve using the quadratic formula. \[ \begin{array}{l}x^{2}+4 x=-12 \\ \text { Select the correct choice below and, if necessary, fill in the answer box within your choice. } \\ \text { A. } x=\square \\ \text { (Simplify your answer. Use a comma to separate answers as needed.) } \\ \text { B. There are no real solutions. }\end{array} \text {. } \]

6. \( |7 x|=-63 \)

2. Make \( \pi \) the subject of the formular \( =\frac{6}{2 \pi} \)

Write out in full and verify the statements \( S_{1}, S_{2}, S_{3}, S_{4} \), and \( S_{5} \) for the follow \( 18+54+90+\cdots+(36 n-18)=18 n^{2} \) \( 18+54+90+126+162=\square \) (Do not simplify.) Are \( S_{1}, S_{2}, S_{3}, S_{4} \), and \( S_{5} \) true statements? No Yes Which of the following is the next step of the proof? A. Show that \( S_{k+1} \) is true. B. Show that if \( S_{k} \) is true, then \( S_{k+1} \) is true. C. Show that \( S_{n} \) is true. O D. Show that if \( S_{k+1} \) is true, then \( S_{k} \) is true. Write the statement \( S_{k} \) and \( S_{k+1} \).

Transpose \( V=\frac{1}{3} \pi r^{2} h \) for \( h \)

4. Transpose \( I=\frac{E-e}{R+r} \) for \( E \)