Tolong dong dijawab no 23 saja tapi pakai cara kerja ya

misal bilangan itu a dan b, maka
a - b = 1 => a = 1 + b
a×b = (1 + b) b. misal perkalian =>P(b)
P(b) = b + b^2
P'(b) = 1 + 2b
1 + 2b = 0
2b = -1
b = -1/2
P(-1/2) = (-1/2) + (-1/2)^2
= -1/2 +1/4
= -2/4 +1/4
= -1/4