▁the ▁highest ▁or ▁lowest ▁value ▁of ▁an ▁objective ▁function . ▁ ▁Some ▁problems ▁specify ▁that ▁one ▁or ▁more ▁of ▁the ▁variables ▁are ▁const rained ▁to ▁take ▁on ▁integer ▁values . ▁ ▁An ▁integer ▁constraint ▁leads ▁to ▁integer ▁programming ▁and ▁Di oph antine ▁equations ▁problems , ▁which ▁may ▁have ▁only ▁a ▁finite ▁number ▁of ▁solutions . ▁ ▁Another ▁kind ▁of ▁constraint , ▁which ▁appears ▁in ▁coding ▁theory , ▁especially ▁in ▁error ▁correct ing ▁codes ▁and ▁signal ▁processing ▁( for ▁example ▁com pressed ▁sens ing ), ▁consists ▁in ▁an ▁upper ▁bound ▁on ▁the ▁number ▁of ▁variables ▁which ▁may ▁be ▁different ▁from ▁zero . ▁In ▁error ▁correct ing ▁codes , ▁this ▁bound ▁corresponds ▁to ▁the ▁maximal ▁number ▁of ▁errors ▁that ▁may ▁be ▁corrected ▁simultaneously . ▁ ▁See ▁also ▁ ▁Over det erm ined ▁system ▁Reg ular ization ▁( math emat ics ) ▁ ▁References ▁ ▁Category : Linear ▁algebra ▁Category : Equ ations <0x0A> </s> ▁The ▁Sa ab ▁ 9 - 7 X ▁is ▁a ▁mid - size ▁lux ury ▁SU V ▁that ▁was ▁built ▁by ▁General ▁Mot ors ▁for ▁the ▁American ▁market ▁and ▁sold ▁under ▁the ▁Sa ab ▁marque . ▁The ▁ 9 - 7 X ▁was ▁first ▁revealed ▁at ▁the ▁ 2 0 0 4 ▁New ▁York ▁International ▁Auto ▁Show , ▁and ▁was ▁available ▁starting ▁in ▁the ▁model ▁year ▁of ▁ 2 0 0 5 , ▁as ▁a ▁replacement ▁for ▁the ▁Old sm obile ▁Bra v ada . ▁ ▁Information ▁and ▁vehicle ▁details ▁ ▁The ▁Sa ab ▁ 9 - 7 X ▁was ▁introduced