simplify [sqrt(17)+sqrt(7)]*[sqrt(17)-sqrt(7)]

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simplify [sqrt(17)+sqrt(7)]*[sqrt(17)-sqrt(7)]

i have to simplify [sqrt(17)+sqrt(7)]*[sqrt(17)-sqrt(7)]

does that mean multiply it out? how do i do that?
buddy

Posts: 141
Joined: Sun Feb 22, 2009 10:05 pm

buddy wrote:simplify [sqrt(17)+sqrt(7)]*[sqrt(17)-sqrt(7)]

Yes, you need to multiply this out. But it's a pretty simple thing to do, if you recognize that this is the factored form of a difference of squares.

. . . . .$a^2\, -\, b^2\, =\, (a\, +\, b)(a\, -\, b)$

Letting $a\, =\, \sqrt{17}$ and $b\, =\, \sqrt{7}$, what do you get?

stapel_eliz

Posts: 1720
Joined: Mon Dec 08, 2008 4:22 pm

Re: simplify [sqrt(17)+sqrt(7)]*[sqrt(17)-sqrt(7)]

17-7=10?
buddy

Posts: 141
Joined: Sun Feb 22, 2009 10:05 pm

buddy wrote:17-7=10?

Yup!

stapel_eliz

Posts: 1720
Joined: Mon Dec 08, 2008 4:22 pm