-x2 - 4x + 21
Factorise

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  -(x -3)(x +7)

Step-by-step explanation:

Apparently, you're supposed to match the given expression with the parts of the identity ...

  (x + a)(x + b) = x² +(a +b) +ab

First of all, we notice that the sign of x² in our given expression is negative. So, we factor -1 out of the expression first.

  -x² -4x +21 = -(x² +4x -21)

Now, matching the coefficients of x, and the constant to those in our identity, we see ...

  a + b = 4 . . . . . coefficients of x

  ab = -21 . . . . . . constants

It is relatively easy to find the factors of -21. We are interested in those factor pairs such that the sum is positive:

  -21 = -1(21) = -3(7) = -7(3) . . . . at this point the sum -7+3 becomes negative

The factor pair a=-3, b=7 will satisfy ...

  a + b = -3 + 7 = 4

  ab = (-3)(7) = -21

So, our factorization is ...

  -x² -4x +21 = -(x² +4x -21) = -(x -3)(x +7)

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8

step-by-step explanation:

to find the amount of gift bags to use all the supplies, find the gcf or greatest common factor. this is the largest number which multiplies evenly into each term.

48 has factors: 1, 2, 3, 4, 6, 8, 12. 16, 24, 48

80 has factors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80

64 has factors: 1, 2, 4, 8, 8, 16, 32, 64

the highest number factor they all share in common is 8. this means there will be 8 bags with 6 pencils, 10 markers, and 8 stickers in each bag.