Simplify a − 2a + 3a − 4a + 5a − 6a + … + 99a − 100a

Question

Thankyou <33

Answer 1

a(1-2 + 3-4 +... + 99-100)
a(-1 + -1 + ... + -1) ---- 50 times
-50a

Answer 2

thankyou :)