Tolong bantu pakai cara nya

Dik:
β= 2α
ΔT= 50 - 20 = 30°C

ΔA= β.Ao.ΔT
= 2.(9 × 10^-6).4.30
= (18 × 10^-6).4.30
= 0,00216 m² = 21,6 cm²