Question

Use any method to multiply (3a + 2b – c)(a – b + 2c).

Question 5 options:

A)

3a2 – 2b2 – 2c2 – ab + 5ac + 5bc

B)

3a2 + 2b2 + 2c2 – ab – 5ac + 5bc

C)

3a2 + 2b2 – 2c2 + ab + 5ac + 5bc

D)

3a2 – 2b2 – 2c2 + ab + 5ac – 5bc

Answer 1

option a is correct

Explanation:

(3a + 2b - c)(a - b + 2c)

3a(a- b + 2c) +2b(a - b + 2c) - c(a - b + 2c)

multiply the brackets

3a^2 - 3ab + 6ac + 2ab - 2b^2 + 4bc - ac + bc - 2c^2

combine like terms

3a^2 - ab + 5ac - 2b^2 + 5bc - 2c^2

3a^2 - 2b^2 - 2c^2 - ab + 5ac + 5bc

Answer 2

A)

3a2 – 2b2 – 2c2 – ab + 5ac + 5bc

`(3a + 2b - c)(a - b + 2c) \\ = (3 {a}^(2) - 3ab + 6ac + 2ab - 2 {b}^(2) + 6bc - ac + bc - 2 {c}^(2) ) \\ = 3 {a}^(2) - ab + 5ac - 2 {b}^(2) + 5bc - {2c}^(2) \\ = 3 {a}^(2) - 2 {b}^(2) - {2c}^(2) - ab + 5ac + 5bc`