a squash plant is homozygous for white is crossed with one homozygous for yellow, what'll be the appearance ?

Question

of the f1? of the f2? of the offspringof across of the f1 back to its white parents? of the offspring of a cross of the f1 back to its parent?

Answer 1

We need to know more information in order to answer this question, specifically which trait is dominant and which is recessive.

Answer 2

In summer squash, yellow is dominant and white is recessive. Does the problem say this? If you don't know which is dominant, you can work out the genotypes, but you won't know which phenotypes will be expected.

R=yellow
r = white

Parents: RR x rr (Homozygous means the alleles match.)
F1: all Rr (each gets R from one parent and r from the other)

Get the F2 by crossing F1 individuals Rr x Rr. Form the gametes and get the results on the Punnett square.
F2 results: RR, Rr, rR, rr
F2 phenotype ratio or appearance: 3 yellow: 1 white

F1 backcrossed with white parent is Rr x rr. Again form the gametes and get the results on the Punnett square.
Offspring turn out to be Rr, Rr, rr, rr.
Appearance or phenotype ratio is 1 yellow: 1 white.

F1 backcrossed with yellow parent is Rr x RR
Offspring are RR, RR, rR, rR.
Appearance of offspring: all yellow.