경사상승법.js

const original = (x) => (x - 1) * (x - 2) * (x - 3) * (x - 4)
const h = 1e-8

const prime = (f => x => (f(x + h) - f(x)) / h)(original)

let max = 100
let max_x = -1
for (let i = 0; i <= 10; i += 0.00005) {
    const res = Math.abs(prime(i))
    if (res < max) {
        max = res
        max_x = i
    }
    if (res.toFixed(3) === "0.000") console.log(i, res.toFixed(8))
}
// x, f(x), f'(x)
console.log(max_x.toFixed(3), original(max_x).toFixed(3), max.toFixed(3))