code: function scaleAndAddRow (m, srcRow, destRow, scale) {
    const me = m.elements;
    let i = destRow;
    let j = srcRow;
    let alpha = (scale === undefined ? 1.0 : scale);
    me[i] += me[j] * alpha;
    me[i + 3] += me[j + 3] * alpha;
    me[i + 6] += me[j + 6] * alpha;
  }
docs: Scales and adds the source row to the destination row.
  @memberof Helpers
  @param {Matrix2|Matrix3|Matrix4} m The matrix.
  @param {number} srcRow The original row index.
  @param {number} destRow The destination row index for the sum to be in.
  @param {number} scale The number to scale the source row by.