A quadratc function in x has the value 10 when x = 1 and has minimum value 1 when x = -2 the function is
A
2x2+3x+5
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B
3x2+2x+5
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C
x2+3x+6
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D
x2+4x+5
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Solution
The correct option is Dx2+4x+5 Let quadratic f(x)=ax2+bx+c f(1)=a+b+c=10 f(−2)=4a−2b+c=1 f′(x)=2ax+b (at extremum f′(x)=0) f′(−2)=−4a+b=0 b=4a So a=1,b=4,c=5