Answer:
an=a1+(n-1)d
an=a1+(n-1)-4
an=a1+-4n+4
-11=a1+-4n+4
-a1=11-4n+4
-a1=-4n+11+4
-a1=-4n+15
-a1=-4(10)+15
-a1=-40+15
-a1=-25
-a1/-1=-25/-1
a1=-25
Explanation:
used the formula an=a1+(n-1)d
an is -11 its the value of the last term
a10 is -11
d is -4 which is the common difference
a1 is missing we don't know yet
n is 10 which is we called the number of terms
dont get confused:) goodluck
u can try checking it by adding the common difference until u reach the a10 so u can see if it's correct, for instance as I get 25 as an a1 as an answer is we 25, 21, 17,13,9,5,1,-3,-7,-11
as u can see notice carefully that 25-4=21-4=17,.....until u reached the -11