Q. Determine h′(1) if h(x)=f(g(2−x2)): if g(1)=4, f′(2)=2, g(1)=41, g′(1)=21
Find Derivative at x=1: We need to find the derivative of h(x) at x=1. To do this, we will use the chain rule, which states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function, multiplied by the derivative of the inner function. The function h(x) is a composition of f and g(2−x2), so we will need to differentiate both of these functions and then evaluate at x=1.
Use Chain Rule: First, let's find the derivative of the inner function g(2−x2). We will use the chain rule again, this time for g(2−x2) and the square root function. The derivative of u with respect to u is (1/2)u−1/2, and the derivative of g(2−x2) with respect to x is −2xg′(2−x2) by the chain rule.
Derivative of Inner Function: Now we can write the derivative of the inner function as: 21(g(2−x2))−21∗(−2xg′(2−x2)).
Derivative of Outer Function: Next, we need to find the derivative of the outer function f(u) with respect to u, which is simply f′(u). We will evaluate this derivative at u=g(2−x2).
Evaluate at x=1: Now we can write the derivative of h(x) as: h′(x)=f′(g(2−x2))⋅(21)(g(2−x2))−21⋅(−2xg′(2−x2)).
Calculate g(1): To find h′(1), we need to evaluate this expression at x=1. We will need the values of g(1), g′(1), and f′(2) to do this. We are given that g(1)=4, g′(1)=21, and f′(2)=2.
Evaluate f′(2): First, we calculate g(2−12)=g(1)=4. Then we find the square root of this value, which is 4=2.
Evaluate g′(1): Next, we evaluate f′(g(2−12))=f′(2)=2, since we are given that f′(2)=2.
Substitute Values: We also need to evaluate g′(2−12)=g′(1)=21, as given.
Simplify Expression: Now we can substitute all the values into the derivative of h(x) to find h′(1):h′(1)=2×(21)(4)−21×(−2×1×21).
Simplify Expression: Now we can substitute all the values into the derivative of h(x) to find h′(1):h′(1)=2×(21)(4)−21×(−2×1×21).Simplifying the expression, we get:h′(1)=2×(21)(21)×(−2×1×21)=2×(41)×(−1)=−21.
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