the square root of x+4 = x-8? I'm doing a summer math packet and this is one problem that really stumped me...

Question

hartnn · Answer

to get rid of square root,square both sides
because $$(\sqrt{a})^{2}=a$$

anonymous · Answer

can you explain that a bit more?

anonymous · Answer

since x+4 is already squared, would i also square x-8?

hartnn · Answer

your question is $$\sqrt{x+4}=x+8$$ isn't it?
squaring both sides will give
$$x+4=(x+8)^{2}$$

anonymous · Answer

right...

anonymous · Answer

then, would i say: x+4 = (x-8)(x-8)?

hartnn · Answer

yes,go on and multiply (x-8)(x-8)

anonymous · Answer

using the FOIL method, right?

hartnn · Answer

u work it out and show the result,i'll tell u whether its correct...

anonymous · Answer

k

anonymous · Answer

x+4=x squared - 8x - 8x + 64
then... x+4=x squared -16x + 64

anonymous · Answer

$$x ^{2} -16x +64$$

anonymous · Answer

right. so, what do i do next?

hartnn · Answer

yes thats correct for (x-8)(x-8)
now equate it to x+4
combine like terms and form a quadratic equation...try

anonymous · Answer

what do you mean by "equate it to"?

hartnn · Answer

$$x+4=x ^{2}-16x+64$$
i meant this

hartnn · Answer

now can u combine terms with x and constants?

anonymous · Answer

answer is x=12 i got it only by checking.yet one another value must satisfy the same relation because is quadratic equation

anonymous · Answer

oh, yeah, i already got that when i solved: (x-8)(x-8)

anonymous · Answer

combine terms? do you mean combining x with -16x and 4 with 64?

anonymous · Answer

i got x squared - 15x + 68

anonymous · Answer

|dw:1345324118065:dw|