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Gujarati JEE Mathematics : દ્વિઘાત સમીકરણ

Multiple Choice Questions

11.
જો કોઈ દ્વિઘાત સમીકરણ ax2 + bx + c = 0 નાં બીજનો સરવાળો તે બીજના વ્યસ્તના વર્ગોના સરવાળા જેટલો થાય, તો નીચેનામાંથી ......... સત્ય બને. 
  • b/c સમગુણોત્તર શ્રેણીમાં હોય

  • ab2, a2c તથા bc2 સમાંતર શ્રેણીમાં હોય. 
  • ab2, a2c તથા bc2 સમગુણોત્તર શ્રેણીમાં હોય. 
  • b/c, a/c તથા c/a સમાંતર શ્રેણીમાં હોય. 

12. જો fraction numerator bold x to the power of bold 2 bold space bold plus bold space bold 2 bold x bold space bold plus bold space bold 7 over denominator bold 2 bold x bold space bold plus bold space bold 3 end fraction bold space bold less than bold space bold 6 bold semicolon bold space bold x bold element of bold R હોય, તો x ની ...... કિંમતો સત્ય બને.
  • x > 11 અથવા x < -1
  • x > 11 અથવા x<-3/2
  • bold italic x bold less than fraction numerator bold minus bold 3 over denominator bold 2 end fraction અથવા -1 < x < 11
  • આપેલ પૈકી એક પણ નહી 

13. જો x એ કોઈ વાસ્તવિક સંખ્યા હોય, તો fraction numerator bold x to the power of bold 2 bold plus bold 14 bold x bold plus bold 9 over denominator bold x to the power of bold 2 bold plus bold 2 bold x bold plus bold 3 end fraction bold space bold element of ....... મળે. 
  • open square brackets bold 1 over bold 3 bold comma bold 3 close square brackets
  • [4,-5]
  • [1, 3]
  • [-5, 4]

14. વિધેય fraction numerator bold 5 over denominator bold 9 bold x to the power of bold 2 bold space bold plus bold space bold 6 bold x bold space bold plus bold space bold 14 end fraction ની મહત્તમ કિંમત ..... છે. 
  • bold 13 over bold 5
  • bold 5 over bold 13
  • 13

  • 5


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15. જો cos α એ દ્વિઘાત સમીકરણ 15x2 + 8x - 12 = 0; 0 < x < 1 નું બીજ હોય, તો bold tan to the power of bold 2 bold alpha over bold 2=...... થાય.
  • 2/3

  • 1/3

  • 5

  • 1/3


16.
જો bold x bold space bold equals bold space square root of bold 20 bold plus square root of bold 20 bold plus end root square root of bold 20 bold plus bold. bold. bold. bold infinity end root end root નું x દ્વારા સમાધાન થતું હોય તો ની કિંમતો ........ હોઈ શકે. (x > 0) 
  • 4, -5

  • 5, -4

  • 4

  • 5


17. સમીકરણ bold 5 to the power of bold 2 bold x to the power of bold 2 bold minus bold 7 bold x bold plus bold 7 end exponent bold space bold equals bold space bold 25 ને ........ બીજ મળે.
  • 0
  • બેથી વધુ 
  • માત્ર બે જ 1 તથા 5/2
  • માત્ર બે જ,  1 તથા 2/3

18. જો x ∈ R હોય, તો fraction numerator bold x to the power of bold 2 bold space bold minus bold space bold 2 bold x bold space bold plus bold space bold 4 over denominator bold x to the power of bold 2 bold space bold plus bold space bold 2 bold x bold space bold plus bold space bold 4 end fraction ની મહત્તમ ન્યુનતમ કિંમત અનુક્રમે ........ હોય.
  • 3, 3
  • bold 1 over bold 3 bold comma bold 1 over bold 3
  • bold 3 bold comma bold 1 over bold 3
  • bold 1 over bold 3 bold comma bold space bold 3

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19. સમીકરણ bold x to the power of begin inline style bold 1 over bold 4 end style bold left parenthesis bold log subscript bold 2 bold x bold right parenthesis bold minus begin inline style bold 3 over bold 4 end style end exponent bold equals bold space bold 2 નાં બીજ .......... મળે. 
  • bold 1 over bold 2 bold comma bold 16
  • bold 1 over bold 16 bold comma bold 2
  • bold 1 over bold 6 bold comma bold 2
  • bold 1 over bold 2 bold comma bold 6

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20.
જો a, b, c ∈ R; a + b + c = 0, c ≠ 0 હોય, તો દ્વિઘાત સમીકરણ 4ax2 + 3bx + 2e = 0 ને ........ બીજ હોય. 
a, c, સમચિહ્ન
  • બે વાસ્તવિક

  • એક ધન તથા એક ઋણ 
  • બે સંકર  
  • બંને શુન્ય.

A.

બે વાસ્તવિક

Tips: -

અહીં 4ax2 + 3bx + 2c = 0 આપેલ છે.

bold therefore bold space bold increment bold space bold space bold equals bold space bold space bold 9 bold b to the power of bold 2 bold space bold minus bold space bold 32 bold ac

            bold equals bold space bold 9 bold left parenthesis bold minus bold a bold minus bold c bold right parenthesis to the power of bold 2 bold space bold minus bold space bold 32 bold ac bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold left parenthesis bold a bold space bold plus bold space bold b bold space bold plus bold space bold c bold space bold equals bold space bold 0 bold space bold rightwards double arrow bold space bold b bold space bold equals bold space bold minus bold a bold space bold minus bold space bold c bold right parenthesis

bold equals bold space bold 9 bold space bold left parenthesis bold a to the power of bold 2 bold space bold plus bold space bold c to the power of bold 2 bold space bold plus bold space bold 2 bold ac bold right parenthesis bold space bold minus bold space bold 32 bold ac bold space

bold equals bold space bold 9 bold a to the power of bold 2 bold space bold plus bold space bold 9 bold c to the power of bold 2 bold space bold minus bold space bold 14 bold ac

bold equals bold space fraction numerator bold 9 bold a to the power of bold 2 over denominator bold c to the power of bold 2 end fraction bold minus fraction numerator bold 14 bold a over denominator bold c end fraction bold space bold plus bold space bold 9

bold equals bold space open parentheses fraction numerator bold 3 bold a over denominator bold c end fraction bold minus bold 7 over bold 3 close parentheses to the power of bold 2 bold space bold plus bold space bold 32 over bold 9 bold space bold greater or equal than bold space bold 32 over bold 9 bold greater than bold 0

આથી દ્વિઘાત સમીકરણને વાસ્તવિક બીજ મળે. 

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