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remark-to-question-195301-and-similar-ones-x-2-y-a-x-y-2-b-a-b-gt-0-how-many-solutions-depending-on-a-b-




Question Number 195356 by MJS_new last updated on 31/Jul/23
remark to question 195301 and similar ones  x^2 +y=a  x+y^2 =b  a, b >0  how many solutions depending on a, b?
remarktoquestion195301andsimilaronesx2+y=ax+y2=ba,b>0howmanysolutionsdependingona,b?
Answered by MJS_new last updated on 31/Jul/23
     y=a−x^2   inserting in the 2^(nd)  equation gives       x^4 −2ax+x+a^2 −b=0    possible cases:    I. 4 distinct real solutions       a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))>0  II. 2 distinct and 1 double real solutions       b≠(4/3)a^2 ∧a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))=0  III. 1 single and 1 triple real solutions       b=(4/3)a^2 ∧a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))=0       ⇔ a=b=(3/4)  IV. 2 distinct real and 1 pair of conjugated        complex solutions       a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))<0
y=ax2insertinginthe2ndequationgivesx42ax+x+a2b=0possiblecases:I.4distinctrealsolutionsa3a2b298ab+b3+27256>0II.2distinctand1doublerealsolutionsb43a2a3a2b298ab+b3+27256=0III.1singleand1triplerealsolutionsb=43a2a3a2b298ab+b3+27256=0a=b=34IV.2distinctrealand1pairofconjugatedcomplexsolutionsa3a2b298ab+b3+27256<0
Commented by MJS_new last updated on 31/Jul/23
with a=11∧b=7 we get case I
witha=11b=7wegetcaseI
Commented by Frix last updated on 31/Jul/23
And without a,b >0?
Andwithouta,b>0?
Answered by MJS_new last updated on 31/Jul/23
without the restriction a, b >0: a, b ∈R  I. 4 distinct real solutions       a>0∧b>0∧a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))<0  II. 2 distinct and 1 double real solutions       a>0∧b>0∧b≠(4/3)a^2 ∧a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))=0  III. 1 single and 1 triple real solutions       a=b=(3/4)  IV. 2 distinct real and 1 pair of conjugated          complex solutions       a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))>0  V. 1 double real and 1 pair of conjugated        complex solutions       a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))=0∧(a<0∨b<0)  VI. 2 pairs of conjugated complex solutions       a^3 −a^2 b^2 −(9/8)ab+b^3 +((27)/(256))<0∧(a<0∨b<0)
withouttherestrictiona,b>0:a,bRI.4distinctrealsolutionsa>0b>0a3a2b298ab+b3+27256<0II.2distinctand1doublerealsolutionsa>0b>0b43a2a3a2b298ab+b3+27256=0III.1singleand1triplerealsolutionsa=b=34IV.2distinctrealand1pairofconjugatedcomplexsolutionsa3a2b298ab+b3+27256>0V.1doublerealand1pairofconjugatedcomplexsolutionsa3a2b298ab+b3+27256=0(a<0b<0)VI.2pairsofconjugatedcomplexsolutionsa3a2b298ab+b3+27256<0(a<0b<0)

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