If (x +5) and (x -3) are the factors of ax2+bx+c, , then values of a, b and c are
A
1,-2,15
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B
1,2,-15
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C
1,2,15
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D
1,2,3
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Solution
The correct option is B 1,2,-15 Given that,
x+5 is a factor,
Let's take p(x)=ax2+bx+cSubstitutex=−5p(−5)=a(−5)2+b(−5)+c=25a−5b+c=0...........(1)
Also x - 3 is a factor. p(3)=a(3)2+3b+c=0c=−9a−3bSubstitutethisin(1)25a−5b=9a+3b25a−9a=3b+5b16a=8bab=816=12Substitutea=1andb=2in(1)25(1)−5(2)=−cc=−15a=1,b=2andc=−15HenceoptionCisthecorrectanswer.