For each case $($a and b$)$ find the equivalent spring constant of the system $($keq$)$ using Lagranges equation $($L$=$T$-$V$)$ to derive the equation of motion. Knowing that with newtons second law the result is : for case a$)$ keq $=$ k$((4$a$^2-$b$^2)/($b$^2))$ and for case b$)$ keq $=$ k