When you multiply or divide a whole number by a power of ten just add the zeros. 5 to the 100000 power is 500000. Five zeros. Hope this helps. Just a little trick and pattern I noticed which helps. :)
c. 9
To complete the square, you take half of the coefficient of b and square it. It's important to note that the value being added will always be positive.





Add together to get -3
Multiply together to get -10
Can you think of the two numbers?
Try 2 and -5:
2+-5 = -3
2*-5 = -10.
Therefore, (x+2)(x-5) is the answer :)