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OpenStudy (anonymous):
any expression multiplied by its reciprocal = 1
eg reciprocal of x = 1/x
x * 1/x = 1
OpenStudy (campbell_st):
if the question is \[(x - 4)/(\sqrt{x} -2) \times (\sqrt{x} -2)/(x-4) \] the answer is 1.
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
i think i used the wrong term... i have to multiply but the opposite of the bottom
OpenStudy (anonymous):
but=by
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OpenStudy (anonymous):
the opposite of the bottom?
OpenStudy (anonymous):
ya so its (x-4)/(sqroot(x)-2)*(sqroot(x)+2)/(sqroot(x)+2)
OpenStudy (anonymous):
hmm maybe you want to simplify by rationalising the denominator
i e multoplying top and bottom by the conjugate of sqrtx - 2 which is sqrtx + 2
so its
(x-4)*(sqrtx + 2) (x-4)(sqrtx+2)
-------------- = ------------ = sqrtx + 2
(sqrtx-2)(sqrtx+2) ( x - 4)
OpenStudy (anonymous):
yes conjugate is the word i was looking for
OpenStudy (anonymous):
the (x-4)'s cancel out and you're left with sqrtx + 2
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