Question

Factorise the following
$(x + y)(a + b) - (y + z)(a + b)$

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Answer 1

= ax + bx + ay + by - ( ay + by + az + bz)

= ax + bx + ay + by - ay - by - az - bz

= - az + ax - bz + bx

= - a(z - x) - b(z - x)

= - (z - x) (a + b)