What should be subtracted from the expression (2x² − x − 5) to obtain the expression (x + 2) (x − 3)?

The required expression can be obtained by subtracting the expression (x + 2) (x − 3) from (2x² − x − 5).

∴ 2x² − x − 5 − {(x + 2) (x − 3)}

= 2x² − x − 5 − {x² + {2 + (−3)} x + 2 (−3)}

= 2x² − x − 5 − (x² − x − 6)

= 2x² − x − 5 − x² + x + 6

= x² + 1

Thus, the required expression is x² + 1.