How do you factor #20x^2 - 5#?

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Answer 1 · 2016-08-29T09:14:43

#20x^2-5=5(4x^(2)-1)# #=# #5(2x-1)(2x+1)#

So we have #20x^2-5=5(4x^(2)-1)#; dividing thru by #5#.

#5(4x^(2)-1)#

And #4x^2-1# is the difference between 2 squares, #2x# and #1#.

#(4x^(2)-1)# #=# #(2x-1)(2x+1)#

Putting it all together:

#20x^2-5=5(2x-1)(2x+1)#

So there are roots at #+-1/2#.