不懂兩題因式分解

ccshong28

Fatorise the following.

3(a-b)+3(b-a)c^4

x^2-(y-z)^2
偶唔知點做

sapphire

Remember that x^2-y^2=(x+y)(x-y)

3(a-b)+3(b-a)c^4
=3(a-b)-3c^4(a-b)
=3(a-b)(1-c^4)
=3(a-b)(1+c^2)(1-c^2)  
=3(a-b)(1+c^2)(1+c)(1-c)

now u should know how to do the 2nd question, try to finish it urself
ans=(x+y-z)(x-y+z)