That approach works too, but here let's use the factor theorem...
Literal
That method [also-も] good [but-けど], here factor-theorem [obj-を] use-[and-て]...
やり方 'way / method / approach' is the compound noun from 遣る 'to do' (masu-stem 遣り) + 方 'way.' 因数定理 'factor theorem' is a mathematics term — 因数 'factor' + 定理 'theorem.' The sentence trails off on ~使って, a casual open-ended te-form that leaves the student to fill in the next step — characteristic of tutoring speech.