The function is defined by f(x)= x^2+3x-10

if f (x+5) = x^2 +kx+30, k=

find the smallest zero of f (x+5). x=

First you put (x+5) into the initial function wherever you see x so it becomes
(x+5)^2+3(x+5)-10=x^2+kx+30
(x^2+5x+25)+(3x+15)-10 simplified left side
x^2+8x+30 fully simplified left side 
thus k=8
x^2+8x+30=0 to find 0s
-4 + 3.7416573867739i
-4 - 3.7416573867739i
these are the roots you find after using the quadratic formula 
the second one is the smallest

(6,0) i hope it makes enough sense