Question

40+3x-x² factorise it
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Answer 1

40 + 3x - x²

-x² + 3x + 40

$a + b = 3$

$ab = - 40 = - 4 0$

- 1 , 40

- 2 , 20

- 4 , 10

- 5 , 8

$- 1 + 40 = 39$

$- 2 + 20 = 18$

$- 4 + 10 = 6$

$- 5 + 8 = 3$

$a = 8$

$b = - 5$

( - x ² + 8x ) + ( - 5x + 40 )

- x ( x - 8 ) - 5 ( x - 8 )

( x - 8 ) ( - x - 5 )