Question

Factorise:
28 − 31x − 5x²

Answer 1

$$\begin{gathered} Thegivenexpressionis28-31x-5x^2. \\ \mathrm{Find}\mathrm{two}\mathrm{numbers}\mathrm{that}\mathrm{follow}\mathrm{the}\mathrm{conditions}\mathrm{given}\mathrm{below}: \\ Sum=-31 \\ Product=28\times -5=-140 \\ Clearly,thenumbersare-35and4. \\ 28-31x-5x^2=28+4x-35x-5x^2 \\ =4(x+7)-5x(7+x) \\ =(x+7)(4-5x) \end{gathered}$$