Question

Factorise by splitting the middle term
2x² +11x-21
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Answer 1

first multiply the x^2 coefficient  and constant = 2 * -21 = -42 (a)
then take the x coefficient = 11 (b)
find two number when multiplied gives a and when added gives b.
so 14 * -3 gives a = -42
14 + -3 gives b = 11
so,substitute 14x-3x in place of 11x
2x^2+14x-3x-21
2x ( x+7) -3 (x + 7) (taking common terms outside)
(2x - 3) (x + 7 )