Question

factorise a^4-20a^2+8

Answer 1

Hi ,

a⁴ - 20a² + 8

= ( a² )² - 2 × a² × 10 + 8

= ( a² )² - 2 × a² × 10 + 10² + 8 - 10²

= ( a² - 10 )² + 8 - 100

= ( a² - 10 )² - 92


= ( a² - 10 )² - ( √ 92 )²

= ( a² - 10 + √92 ) ( a² - 10 - √ 92 )

I hope this helps you.

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