Dimitri is solving the equation x2 – 10x = 21. which value must be added to both sides of the equation to make the left side a perfect-square trinomial?
0
4
25
100

option-C

25

Step-by-step explanation:

we are given

Since, we have to complete square of left side term

so, we can use formula

so, we can split middle terms in 2ab form

we can write as

now, we can compare this with formula and find 'a' and 'b'

we get

a=x and b=5

so, b^2 term is missing to complete square

so, we should add both sides by b^2 or 5^2 because b=5

we get

So, we will add 5^2 or 25

i assume that by 5 you mean 5 gallons.

(20)(0.25) = 15

removing 15 gallons reduces the tank from 20 to 5.

answer: #1 ads up by 8 and i don't know #2