I thought you're pro, but you've showed me another example of no one is perfect ! Hahahaha

I've problems about this too, I just do the way let, and let .. without knowing the logic . Until before SPM, I asked here in LYN !

I got the logic .. actually you don't have to let, just that it will be very hard to figure out the answer .


So for your question, if I don't let ,

h(x+4) = x^2 + 8x + 10
h(x+4) = (x+4)^2 - 6
h(x)=x^2 - 6



This post has been edited by CallMeBin: Jan 15 2012, 10:10 PM

(x+4)^2 = x^2 + 8x + 16


=)

The first one

h(x+4) = x^2 + 8x + 10

The 2nd one

h(x+4) = x^2 + 8x + 16 - 6

Since they're the same equation which is h(x+4), so they must be the same .
(x+4)^2 get x^2 + 8x + 16,
so I must minus 6 to get 10


Oh god, if you really can't explain, don't explain, you will make the newbies confused .

Ok let's see
h[k(x)] , k(x) is the object
So, for convenience, you let y = k(x)
Therefore, h(y)

So continue ,
h(y) = x^2 + 8x + 10

As you can see, Left Equation, the object is y
While, Right equation the object is x
No sense right ? So you must make the object equal

So since k(x) = y = x+4
So now you have to get x instead of y to fulfill the same-object-criteria
Hence, x = y - 4

h(x) = x^2 + 8x + 10
Since, x = y-4
So substitute !

Oh gosh, couldn't believe that I still can explain !