** Chip design software maker Synopsys' SNPS.O shares up 4.3% at $515.78
** Company to buy Ansys ANSS.O in $35 bln cash-and-stock deal
** Ansys shares down 4.4%
** Deal implies per-share value of $390.19 and represents a premium of about 29% over Ansys' last close on Dec. 21, 2023, the companies said
** Transaction would be the biggest acquisition in the technology sector since chipmaker Broadcom AVGO.O took over software maker VMware last November in a $69 billion deal
(Reporting by Pranav Kashyap in Bengaluru)