Q108 / 160 · TS EAMCET 2019 (03 May Shift 2) · Mathematics

Let a, b, c∈ℝ be such that 2a+3b+6c=0 and g(x) be the antiderivative of f(x)=ax2+bx+c. If the slopes of the tangents drawn to the curve y=g(x) at (1,g(1)) and (2,g(2)) are equal, then

  • A
    a3=b-8=c3
  • Correct answer
    B
    a6=b-18=c7
  • C
    a3=b-6=c2
  • D
    a=b=c=-1

Solution

Slopes of tangent of the function gx at x=1 & x=2 implies that f1=f2.

⇒a+b+c=4a+2b+c

⇒3a+b=0  ...i

And 2a+3b+6c=0  ...ii (Given)

Solving equations i & ii by cross-multiplication method we get, 

a6=b-18=c7.

Hence, the correct answer is option: 'B'.

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