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Given the function g(x) = -x² + 3x, which of the following is the correct limit definition of g'(2)?

1) lim(h →0) [(-2(2+h) + 3(2+h) - (-2(2)) + 3(2)) / h]
2) lim(h →0) [(-2(2+h) + 3(2+h) - (-2(2)) + 3(2)) / (2+h)]
3) lim(h →0) [(-2(2) + 3(2) - (-2(2-h)) + 3(2-h)) / h]
4) lim(h →0) [(-2(2) + 3(2) - (-2(2-h)) + 3(2-h)) / (2-h)]

User Ian Wise
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1 Answer

3 votes

Final answer:

The correct limit definition for g'(2) is given by using the difference quotient formula and simplifying it to find the value of the derivative as h approaches 0. Hence, the first option is correct.

Step-by-step explanation:

The correct limit definition of g'(2) for the function g(x) = -x² + 3x is determined by using the difference quotient formula. The definition of a derivative at a point x=a is the limit as h approaches 0 of the function (g(a+h) - g(a))/h. Therefore, for calculating g'(2), the correct expression using the limit definition is:


lim(h →0) [g(2+h) - g(2)] / h


where g(2+h) = -(2+h)² + 3(2+h) and g(2) = -2² + 3(2). So, the expanded form will be lim(h →0) [(-2(2+h) + 3(2+h)) - (-4+6)] / h, which simplifies down to:


lim(h →0) [(-4 - 2h + 6 + 3h) - (2)] / h


lim(h →0) [(-4 - 2h + 6 + 3h + 4 - 6) / h]


lim(h →0) [h] / h = lim(h →0) 1

Thus, the first option is correct: 1) lim(h →0) [(-2(2+h) + 3(2+h) - (-2(2)) + 3(2)) / h].

User Thomas Taylor
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7.8k points