For all integer values of x and constant k, if (x-k)(x-5)=x^2-9x+20, what is the value of K? A) -5
B) -4
C) 4
D) 10
E) 12

Work Shown:

Expand out the left hand side

(x-k)(x-5)

x(x-5)-k(x-5)

x^2-5x-kx+5k

Note that the constant term here is 5k. Yes k seems like a variable, but it's actually a constant. Once we know k, we can replace it to get a fixed number. In this case, k = 4 since 5k = 5*4 = 20 to have it match with the 20 at the end of x^2-9x+20

For the x terms, we have -5x-kx = -5x-4x = -9x which matches with the middle term of x^2-9x+20

Therefore,

(x-k)(x-5) = x^2-9x+20

updates to

(x-4)(x-5) = x^2-9x+20

The -4 and -5 multiply to 20, and they also add to -9. This helps confirm we have the right k value.

i think c. but don't trust it.

step-by-step explanation:

walter needs to make at least 5 more cookies but no more than 40. 5 ≥ x ≥ 40;

step-by-step explanation:

walter has to make a minimum of 20 cookies. he already has 15 cookies made, so he must make 5 more to meet the minimum.

the maximum amount of cookies he can make is 55. he already has 15, so he has to make no more than 40 more cookies to meet the maximum.