9999 is largest 4 digit number, and 100^2 is 10000, or 1 greater than the largest 4 digit number. This means that the closest square root of the largest perfect square is most likely 99. So 99^2 (9801)is the largest perfect square of four digits.
True.....I am not really good at explaining, but I would try. for any fraction , if it is multiplied by it inverse it equals to one because they end up crossing out. example: 3/4 ×4/3=1
6/23×23/6=1
Multiply first equation by -5 and 2nd by 2, add them
15x+20y=-100
<u>2x-20y=32 +</u>
17x+0y=-68
17x=-68
divide both sides by 17
x=-4
the x value is -4
A would be fine as your answer.