Помогите плиззз..Очень нужно...

y =14cosx+7√3x -7√3π/3 +6. ; x∈[ 0;π/2]
----------------------------------------------------
max(y )  --?
y'(x) = -14sinx+7√3  = -14(sinx -√3/2).
y'(x)=0 ;
sinx=√3/2     *** x= (-1)^k +π*k ,k ∈Z  ***
x =π/3 ∈[0;π/2]
-----------------------------------------------------------------------
y(a) =y(0) =14cos0  +7√3*0  -7√3π/3+6  = 20 - 7√3π/3 ;
y(π/3) =14cosπ/3 +7√3*π/3 -7√3π/3+6 =13  ;
y(b) =y(π/2) =14cosπ/2   +7√3*π/2 -  7√3*π/3 +6= 7√3*π/2 -  7√3*π/3 +6

max(y ) =  y(π/3)  =13.