Solve for x.

x2 + 4x - 21 = 0

a.

-3, -7

b.

-3, 7

c.

3, -7

d.

3, 7

C.  3, -7

Step-by-step explanation:

x^2 +4x-21 =0

Factor

What 2 numbers multiply to -21 and add to 4

7*-3 = -21

7-3 = 4

(x+7) (x-3) =0

Using the zero product property

x+7 =0       x-3=0

x+7-7=0-7     x-3+3=0+3

x = -7            x=3

Step-by-step explanation:

matrix of mxn multiplied by another of nxp gives a matrix of mxp. the product does not have to be a square matrix. for example, a(4,2)*b(2,6) => ab (4,6), a rectangular matrix with 4 rows and 6 columns.