Find and correct the errors in the following mathematical statement.
(a - 4) (a -2) = a2 - 8
Factorise: 27x3 - 21x2 + 15x4
We have 27x3 = 3 × 3 × 3 × x × x × x
21x2 = 3 × 7 × x × x
15x4 = 3 × 5 × x × x × x × x
We get common factors as 3, x and x.
i.e. 3 × x × x or 3x2
∴ 27x3 = 3x2 × 3 × x × 3 = 3x2 × 9x
21x2 = 3x2 × 7 = 3x2 × 7
15x4 = 3x2 × 5 × x × x = 3x2 × 5x2 27x3 - 21x2 + 15x4 = (3x2 × 9x) - (3x2 × 7) + (3x2 × 5x2)
= 3x2[9x - 7 + 5x2]