Ricardo says that the expression y+4 is equivalent to the expression 1y+4. is he correct? explain

Yes because there is an invisible one in fron to y

1y means 1 times y

basically you can multiply 1 times anything and it will remain the same so therefor

y=1y = (1) (y) = (1) (1) (y) = (1) (1) (1) (y) = (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (y) etc

so basically he is correct since y=1y so therefor

y+4=1y+4

subtract 4 from both sides

y=1y

subsitute

y=1y

1y=1y

true

Correct! That is because next to every variable is an invisible 'one'. So that means that their is one 'y'.

y + 4 = 1y + 4