d) (5x+3) ( 4x-1) +(10x-7) (-2x+3) =27

e)(8x-5) (3x+2) -(12x+7) (2x-1)=17

f) (5x+9) (6x-1) -(2x-3)( 15z+1) = -190

g) 6x(5x+3) + 3x(1-10x) =7

h) (3x-3) (5 -21x) +(7x+4)(9x-5) =44\

i) (x+1)(x+2)(x-5)-x² (x+8)=27

Chứng minh rằng

a) ( 3x + 2y) (5x - y) - y² = 15x² + 7xy- 3y²

b) 2x² + 5xy + 3y² = 4x² - ( x -3y) (2x+y)

c) (x+y) (x-y) - 9y² = ( x-2y) (x + 5y) - 3xy

a) 5x(12x+7) - 3x(20x-5)= -100

b) 0,6x(x-0,5) - 0,3x(2x+1,3)= 0,138

c) 4x(3x-7) - 6(2x² - 5x + 1) =12