Answer
a. $(x^2 + 1)^{24}/24 + C$
b. $−(cos^{4}x)/4 + C$
Work Step by Step
a. Considering u=($x^{2}+1$)
therefore $du=2x dx$
So by substituting, we get,
$\int u^{23}du = u^{24}/24 + C$
b. Considering $u=cosx$
therefore $du=-sinx dx$
So by substituting, we get,
$−\int u^3du = −u^4/4 + C$