How do you factor #-5a ^ { 7} + 20a ^ { 6} - 20a ^ { 5}#?

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Answer 1 · 2017-05-15T12:26:32

#-5a^5(a-2)^2#

When factorising, first look for common factors.

#-5a^7+20a^6-20a^5#

Here we have #-5a^5# as the GCF

#-5a^5(a^2-4a+4)#

then look to see if the bracket can be factorised separately

we note it is a quadratic, and a perfect square at that

#-5a^5(a-2)^2#