英文關鍵字
background
chalkboard
education
math
school
abstract
formula
equation
geometry
university
blackboard
number
physics
mathematical
classroom
design
technology
symbol
business
calculating
chalk
drawing
blue
illustration
science
concept
graphic
art
sign
vector
animation
research
studying
chemistry
data
mathematics
study
theory
abstraction
light
text
information
pattern
algebra
motion