Question

factorise 2x²-7x-39 using factor theorem​

Answer 1

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We try to find two numbers p and q such that p+q=−7 and p×q=2×(−39)=−78. We can take p=−13 and q=6 as −13+6=−7 and (−13)×6=−78.

Thus we write

2x2−7x−39=2x2−13x+6x−39=x(2x−13)+3(2x−13)=(x+3)(2x−13)