SOLUTION: please help me with this problem, Multipy (3sqrt2 - 6sqrt7)(4sqrt2 + 8sqrt7)= I came up with -312 It said to simplify my answer and type exact answer using radicals as n

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: please help me with this problem, Multipy (3sqrt2 - 6sqrt7)(4sqrt2 + 8sqrt7)= I came up with -312 It said to simplify my answer and type exact answer using radicals as n      Log On


   

Question 516154: please help me with this problem,

Multipy
(3sqrt2 - 6sqrt7)(4sqrt2 + 8sqrt7)=
I came up with -312
It said to simplify my answer and type exact answer using radicals as needed, I need to submit by 3am est. If anyone can and show me how they worked it I appreciate it, if not, that is ok too.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+%28+3sqrt2+-+6%2Asqrt7+%29%2A%28+4%2Asqrt2+%2B+8%2Asqrt7+%29+
Follow the rule:
+%28+a+-+b+%29%2A%28+c+%2B+d+%29+=+a%2Ac+-+b%2Ac+%2B+a%2Ad+-+b%2Ad+

+12%2Asqrt%284%29+-+24%2Asqrt%2814%29+%2B+24%2Asqrt%2814%29+-+48%2Asqrt%2849%29+
+12%2A2+-+48%2A7+
+24+-+336+
+-312+
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That is if only the positive square roots are required.
Usually that's true.