  We prove that a bivariate polynomial f with exactly t non-zero terms,
restricted to a real line {y=ax+b}, either has at most 6t-4 zeroes or vanishes
over the whole line. As a consequence, we derive an alternative algorithm to
decide whether a linear polynomial divides a bivariate polynomial (with exactly
t non-zero terms) over a real number field K within [ log(H(f)H(a)H(b)) [K:Q}]
log(deg(f)) t]^{O(1)} bit operations.
