Question

lit ( f(x)=9 x+6 )
( f^{prime}(x)=a )
given ( f(x)+f^{prime}(x)=x )
( quad ) ax ( x+6=x )
so ( (9=1) mid begin{array}{c}a+6=0 6=7end{array} )
( f(x)=x-1 )
( f(4)=4-1=3 )

# Let f(x) be a polynomial function satisfying f'(x) + f(x)=x. Then the value of f(4) is equal to (1) 1 (4) 4 (2) 2 (3)3

Solution