Factorise: 1) x4 - 14x2 + 1
2) (x2 - 2x)2 - 23(x2 - 2x) +120
(x² - 2x)² - 23(x² - 2x) + 120
(x² - 2x) = a
a²-23a + 120
a²-15a – 8a + 120
a(a-15) – 8(a-15)
(a-15)(x-8)
put the value of a
(x² - 2x – 15)( x² - 2x -8)
(x² - 5x + 3x – 15)(x² - 4x + 2x – 8)
[x(x-5) + 3(x-5)] [x(x-4) + 2(x-4)]
(x-5)(x+3)(x-4)(x+2) ans