F(1)=-8
f(n)=f(n-1)-3
Find the explicit formula
Will mark Brainiest

f(1) = -8, simply is a way of saying, the 1st value in the arithmetic sequence is -8.

f(n) = f(n-1) - 3, is another way of saying, following values are just, the previous minus -3.

so in short, -3 is the common difference, since that is what we're "adding" to get the new value in the sequence.

m∠a is 90°

m∠b is 40°