$x\left(t\right)=\frac{t}{k}-\frac{1}{k^2}+ce^{-kt}$

$\left(\frac{1}{2}x-x^2\right)^2$

$-49+7\cdot\left(-5\right)$

$-3\cos\left(x\right)=-11\cos\left(x\right)-4$

$+5+12+9+8+11$

$\int\frac{sec\left(x\right).\tan\left(x\right)}{\sqrt{\sec^2\left(x\right)+1}}dx$

$6b-2a$