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Find the number of points of local extrema of `f(x)=3x^4-4x^3+6x^2+ax+b` where `a,b in R` |
Answer» We have `f(x) = 3x^(4) - 4x^(3) + 6x^(2) + ax + b` `therefore (dy)/(dx) = 12x(x^(2) - x + 1) + a` `rArr (d^(2)y)/(dx^(2)) = 12(3x^(2) - 2x + 1) gt 0` So, `(dy)/(dx)` is an increasing function. But `(dy)/(dx)` is polynomial of degree 3. So, it has exactly one real root. Thus, derivative becomes zero at exactly one point. |
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