Answer:
x = -2
Step-by-step explanation:
![f(x) =x^2 -2x\:\: and \:\: g(x) = 6x + 4\\(f+g)(x) = f(x) + g(x) \\(f+g)(x) = x^2 -2x+ 6x + 4\\(f+g)(x) = x^2+4x + 4\\(f+g)(x) = (x+2)^2\\ 0 = (x+2)^2...[\because (f+g)(x) =0]\\0 = x+2\\\therefore x = -2](https://tex.z-dn.net/?f=f%28x%29%20%3Dx%5E2%20-2x%5C%3A%5C%3A%20and%20%5C%3A%5C%3A%20g%28x%29%20%3D%206x%20%2B%204%5C%5C%28f%2Bg%29%28x%29%20%3D%20f%28x%29%20%2B%20g%28x%29%20%5C%5C%28f%2Bg%29%28x%29%20%3D%20x%5E2%20-2x%2B%206x%20%2B%204%5C%5C%28f%2Bg%29%28x%29%20%3D%20x%5E2%2B4x%20%2B%204%5C%5C%28f%2Bg%29%28x%29%20%3D%20%28x%2B2%29%5E2%5C%5C%200%20%3D%20%28x%2B2%29%5E2...%5B%5Cbecause%20%28f%2Bg%29%28x%29%20%3D0%5D%5C%5C0%20%3D%20x%2B2%5C%5C%5Ctherefore%20x%20%3D%20-2)
Let the score on her seventh test be "x".
SO,

∴ He must get 104% on his seventh test to get an average score of 90%
Answer:is this true or false or something?
Step-by-step explanation:
Answer:
x + 15
Step-by-step explanation:
Since I don't know what this number is, I'm going to use the variable x to substitute for the value of the unknown number.
So it would just be x + 15 because addition is the operation of adding and the key words are usually more. Since one of the numbers is unknown, we can't get an answer like "100" because x is undefined.
Say x=100, then the number would be written as 115 in it's simplest form but you could also write it as 100+15. So I'm just using substitution.