Function fractionalLinearInnerQ

src/compute-engine/rubi/rubi-utils.ts:2338–2350

True if `u` contains a `Power(base, p)` whose base is LINEAR in `x` and * whose exponent `p` is a POSITIVE non-integer literal (`√(c+d·x)`, * `(c+d·x)^(3/2)`) — the linear-inner shape whose substitution reduction * (4.1.12 #81-86) lands an elementary sin/cos·poly antiderivative. Distinguishes *

(u: Expression, x: string)

  const coeffs = trimZeros(coeffs0);
  const n = coeffs.length - 1;
  if (n <= 2) return null;
  const d = rtExpr(coeffs[n], n);
  const c = coeffs[n - 1].div(ce.number(n).mul(d.pow(n - 1))).evaluate();
  const X = ce.symbol(x);
  const a = safeSimplify(u.sub(c.add(d.mul(X)).pow(n)));
  if (zeroQ(a) || a.has(x)) return null;
  return { a, b: ce.One, c, d, n };
}

/** Rubi FractionalPowerFactorQ: a factor of u is a complex constant or a
 * fractional power */
function fracPowerFactorQ(u: Expression): boolean {
  if (!u.ops) return isNumber(u) && typeof u.im === 'number' && u.im !== 0;
  switch (u.operator) {
    case 'Power': {
      const e = u.ops[1];