Question

What should be added to 1 + 2x – 3x² to get x² – x – 1?

Answer 1

Let the added algebraic expression may be ‘A say

(1 + 2x – 3x²) + A = x² – x – 1

=A =(x² – x – 1) – (1 + 2x – 3x²)

= x² – x – 1 – 1 – 2x + 3x²

= (x² + 3x²) + ( – x – 2x) +( – 1 – 1)

∴ A = 4x² – 3x – 2

∴ The required added expression (A) 

= 4x² – 3x – 2