1) 10-(7-4x-x²)=x²+8x-9;2) (5x²-3)-(2x+5)=5x². ​

1)3

2)-4

1) 10-(7-4x-x²)=x²+8x-9

10-7+4x+x²=x²+8x-9

x²-x²+4x-8x=-9+7-10

-4x=-12 |:(-4)

x=3

:3

2)(5x²-3)-(2x+5)=5x²

5x²-3-2x-5=5x²

5x²-5x²-2x=5+3

-2x=8 |:(-2)

x=-4

:-4