Question

Add the following expressions:

(i) 8a – 6ab + 5b, –6a – ab – 8b and –4a + 2ab + 3b

(ii) 5x³ + 7 + 6x – 5x², 2x² – 8 – 9x, 4x – 2x² + 3 x 3, 3 x 3 – 9x – x² and x – x² – x³ – 4

Answer 1

(i) Given 8a – 6ab + 5b, –6a – ab – 8b and –4a + 2ab + 3b

= (8a – 6ab + 5b) + (–6a – ab – 8b) + (–4a + 2ab + 3b)

Collecting positive and negative like terms together, we get

= 8a – 6a – 4a – 6ab – ab + 2ab + 5b – 8b + 3b

= 8a – 10a – 7ab + 2ab + 8b – 8b

= –2a – 5ab

(ii) Given 5x³ + 7 + 6x – 5x², 2x² – 8 – 9x, 4x – 2x² + 3 x 3, 3 x 3 – 9x – x² and x – x² – x³ – 4

= (5 x 3 + 7+ 6x – 5x²) + (2 x 2 – 8 – 9x) + (4x – 2x² + 3 x 3) + (3 x 3 – 9x-x²) + (x – x² – x³ – 4)

Collecting positive and negative like terms together, we get

5x³ + 3x³ + 3x³ – x³ – 5x² + 2x² – 2x²– x² – x² + 6x – 9x + 4x – 9x + x + 7 – 8 – 4

= 10x³ – 7x² – 7x – 5