Question

(2square root7a)(-4square root7a) solve

Answer 1

2sqrt(7a)*(-4sqrt(7a)) = 2*sqrt(7a)*(-4)*(sqrt(7a)) , which is the associative property of multiplication.

= sqrt(7a)*sqrt(7a)*(2*(-4)) ,which is the commutative property of multiplication

Do you know how to solve that?

Answer 2

I am using hte foil method but Iam stuck when I get multiplying the 2 square roots of 7a together---2(-4) + 2sqrt7a-4sgrt7a +sgrt7asquared does this make since what I am doing

Answer 3

You can't use foil for this. foil is only for (a+b)(c+d). Not for (a*b)*(c*d)

Answer 4

so is my answer -8sqrt49asquared

Answer 5

(a*b)*(c*d) = a*b*c*d = abcd = acbd = bdca
It's both the associative property and commutative property combined

Answer 6

Wrong, but close

Answer 7

See, sqrt(7a)*sqrt(7a) = sqrt(7a*7a) = sqrt( (7a)^2 )

Answer 8

-8sqrt7a^2

Answer 9

what is sqrt(x^2) ?

Answer 10

\[2(-4) +2\sqrt{7a}-4\sqrt{7a}+\sqrt{7a ^{2}}\] I get this far and then I am stuck

Answer 11

That is wrong. You can't use foil. This is pure multiplication, unless you stated your original problem wrong.

Answer 12

the question reads perform the indicated operations and simplify your answer. write your answer in simple radical form\[(2\sqrt{7a})(-4\sqrt{7a)}\]

Answer 13

Yes but this is multiplication

Answer 14

so you can't use foil

Answer 15

-8\[-8\sqrt{49a ^{2}}\] equals 8*7a=56a

my answer is 56a

Answer 16

oops -56a

Answer 17

Which is 99% correct

Answer 18

It is probably good enough for your teacher, but a true mathematician would say this is wrong.

Answer 19

the answer is -56a if a is positive, and 56a if a is negative, because the square root sign is actually a principal square root sign, and it must be positive.