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

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Answer 1 · 2017-05-15T12:26:32

$- 5 a^{5} {(a - 2)}^{2}$ $-5a^5(a-2)^2$

When factorising, first look for common factors.

$- 5 a^{7} + 20 a^{6} - 20 a^{5}$ $-5a^7+20a^6-20a^5$

Here we have $- 5 a^{5}$ $-5a^5$ as the GCF

$- 5 a^{5} (a^{2} - 4 a + 4)$ $-5a^5(a^2-4a+4)$

then look to see if the bracket can be factorised separately

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

$- 5 a^{5} {(a - 2)}^{2}$ $-5a^5(a-2)^2$

How do you factor −5a7+20a6−20a5-5a ^ { 7} + 20a ^ { 6} - 20a ^ { 5}?