Which expression is a factor of 21 x2 + 13 x-20

(7x−5)(3x+4)

Step-by-step explanation:

I think this is the answer

(7x−5)(3x+4)

Step-by-step explanation:

Step-1 : Multiply the coefficient of the first term by the constant   -21 • 20 = -420

Step-2 : Find two factors of  -420  whose sum equals the coefficient of the middle term, which is   13 .

     -420    +    1    =    -419

     -210    +    2    =    -208

     -140    +    3    =    -137

     -105    +    4    =    -101

     -84    +    5    =    -79

     -70    +    6    =    -64

     -60    +    7    =    -53

     -42    +    10    =    -32

     -35    +    12    =    -23

     -30    +    14    =    -16

     -28    +    15    =    -13

     -21    +    20    =    -1

     -20    +    21    =    1

     -15    +    28    =    13    That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -15  and  28

                    -21x2 - 15x + 28x + 20

Step-4 : Add up the first 2 terms, pulling out like factors :

                   -3x • (7x+5)

             Add up the last 2 terms, pulling out common factors :

                   4 • (7x+5)

Step-5 : Add up the four terms of step 4 :

                   (-3x+4)  •  (7x+5)

ca = ec

cpctc makes it so that corresponding parts of the triangle you proved to be equal are equal, the other options aren't part of the part of the triangles you proved to be equal.