How do i factorise x^2+6x-40 ?

9514 1404 393

  (x +10)(x -4)

Step-by-step explanation:

Compare the factored and expanded forms:

  (x +p)(x +q) = x^2 +(p+q)x +pq = x^2 +6x -40

That is, the constants in the binomial factors will be factors of -40 that have a sum of 6. This is where your knowledge of multiplication tables is helpful.

  -40 = -1×40 = -2×20 = -4×10 = -5×8

The sums of these factor pairs are 39, 18, 6, 3, respectively. So, the one we want is (-4)(10) = -40. Now that we know the values of 'p' and 'q', we can write the factorization ...

  x^2 +6x -40 = (x -4)(x +10)

7. 153.86 ft

8. 12.56 ft

9. 78.5 m

10. 379.94 in

11. 132.665 m

12. 12.56 yd

13. 226.865 ft

14. 113.04 ft

15. 63.585 ft

16. 254.34 m

17. 50.24 cm

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the 3rd option is right

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