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Consider using the Intermediate Value Theorem (IVT) to find an interval of length ; containing a root of f() =x 4+2x41. Let f(x) = x + 2x + 1. Observe that f(1) = 2 and f (0) = 1. Since f is continuous, we may conclude by the IVT that f has a root in [1,0]. Now, f (-}) =}- Therefore, the IVT guarantees that f has a root on [-1,-+] . Is this method valid? If not, identify the error with this approach. () This method is not valid, to apply the IVT the function value must have opposite signs on the endpoints of the interval. c This method is valid, since the function contains a root on the interval [1,0]. O This method is valid, since the the function is continuous. ) This method is not valid, you must graph the function f(x) = x + 2x + 1 to identify roots of the equation