25d^2-30d-35d+42=25d^2-65d+42.
Start by proving to them that the number 0.57 can be converted into a fraction . A whole number can't exactly be put in to a fraction. 0.57 can be converted to 14.25/25. This information means that 0.57 IS a rational number. Hope this convinced them!
A percent is a number out of 100, so you'd want to multiply the denominator to get 100. In this case, 25 would have to be multiplied by 4 to get 100. To keep the fractions equal to each other, you have to multiply the numerator by the same thing. 2*4=8. Therefore, your fraction would be 8/100 or 8%
X^2+x-30 -- find two numbers that add to one and multiply to -30, which would be 6 and -5. so now you have x^2+6x-5x-30. factor out x and 5 to get x(x+6)-5(x+6). so you get (x+6)*(x-5)
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