(5x^2-2x+1)-(x^2+7x-4)?

First problem:
4/X = (9/5) - ((7X-4)/5X)
4 = 9X/5 - ((7X-4)/5)
20 = 9X - (7X-4)
20 = 9X - 7X - 4
24 = 2X
X = 12

Second problem:
(2X - 5)(X+1) = 2
2X^2 + 2X - 5X - 5 = 2
2X^2 - 3X - 7 = 0
Using the quadratic formula:
X = (3 +/- sqrt((-3)^2 - 4*2*(-7))) / (2*2)
X = (3 +/- sqrt(9+56)) / 4
X = (3 +/- sqrt(65)) / 4

Third problem:
(3X-9Y) / (9Y^2 - X^2)
= -3(3Y-X) / ((3Y+X)*(3Y-X))
= -3 / (3Y+X)

I will tell you.

(5x^2 - 2x + 1) - (x^2 + 7x - 4)
5x^2 - x^2 - 2x - 7x + 1 + 4
= 4x^2 - 9x + 5

4x² - 9x + 5

(5x^2 - 2x + 1) - (x^2 + 7x - 4) = 4x^2 - 9x - 3

(5x^2 - 2x + 1) - (x^2 + 7x - 4)
= 5x^2 - 2x + 1 - x^2 - 7x + 4
= 5x^2 - x^2 - 2x - 7x + 1 + 4
= 4x^2 - 9x + 5
= 4x^2 - 4x - 5x + 5
= (4x^2 - 4x) - (5x - 5)
= 4x(x - 1) - 5(x - 1)
= (x - 1)(4x - 5)

4x^2-9x+5

42x

4x^2 + 5x +5