7.x≥ 1 and X < 4.4, so the integer solution is 1, 2, 3, 4, and its sum is 10.
9. Substitute AB into the linear equation to get y = 5/3x+5, where -kx-b < 0 means kx+b > 0,5/3x+5 > 0, and the solution is x >-3.
10.2 20 12 power +(-2) 20 1 power =2*2 20 1 1 power+(-2) 201.
15.x is less than-1.5, so the largest integer solution is -2.
18.x=(2m- 1)/5,y=(m+2)/5。 Because x+y > 0,2m-1+m+2 > 0,m >-1/3.