6.
1) x²+8x+16-x²=2x+1
8x+16=2x+1
8x-2x=1-16
6x=-15
x=-15:6
x=-2.5
2) x³-2x=x³+8
2x=-8
x=-8:2
x=-4
3) x²+5x-4x-20-x²+18=0
x-2=0
x=2
4) x²-49-(x²-6x+9)=53
x²-49-x²+6x-9=53
6x-58=53
6x=53+58
6x=111
x=111:6
x=18.5
5)x(x-7)(x+7)=0
x=0
x-7=0
x=7
x+7=0
x=-7
6)(x-2+x+2)((x-2)²-(x+2)(x-2)+(x+2)²)=2x³-2x+3
2x(x²-4x+4-(x²-4)+x²+4x+4)=2x³-2x+3
2x(x²-4x+4-x²+4+x²+4x+4)=2x³-2x+3
2x(x²+12)=2x³-2x+3
2x³+24x=2x³-2x+3
26x=3
x=3/26
7)7x²=4x²+4x+1+3x²-5
7x²=7x²+4x-4
4x-4=0
4x=4
x=4:4
x=1
8) x²+3x-2x-6-(x²-3x+2x-6)-5=6x+7
x²+x-6-x²+x-5=6x+7
2x-11=6x+7
6x-2x=-11-7
4x=-18
x=-18:4
x=-4.5
9) x²(x-3)+2(x-3)=0
(x²+2)(X-3)=0
x-3=0
x=3
10) x²(x+2)-9(x+2)=0
(x²-9)(x+2)=0
(x-3)(x+3)(x+2)=0
x-3=0
x=3
x+3=0
x=-3
x+2=0
x=-2
11) 7-(8x²-8x+2x-2)=10x-8x²
7-(8x²-6x-2)-=10x-8x²
7-8x²+6x+2=10x-8x²
9=10x-6x
4x=9
x=9/4
x=2.25
12) 25-10x+x²-(6x²-4x+3x-2)=2x-5x²
25-10x+x²-(6x²-x-2)=2x-5x²
25-10x+x²-6x²+x+2=2x-5x²
27-9x-5x²=2x-5x²
11x=27
x=27/11
13)2x+3IxI-2=4+4x-2-x
2x+3IxI-2=2+3x
x>0
2x+3x-3x=4
2x=4
x=4:2
x=2
x<0<br>2x-3x-3x=4
-4x=4
x=-1
14) 2Ix-1I-3x-5=2-6x-2-2x
2Ix-1I-3x-5=-8x
2Ix-1I=-5x+5
2Ix-1I=-5(x-1)
x≥1
2(x-1)=-5(x-1)
7(x-1)=0
x=1
x<1<br>2(-x+1)=5(x-1)
-2(x+1)-5(x-1)=0
-2x-2-5x+5=0
-7x=-3
x=3/7
15. 5-4x+3Ix+5I=3-2x+3-3x
5-4x+3Ix+5I=6-5x
3Ix+5I=6-5x-5+4x
3Ix+5I=1-x
x>-5
3x+15=1-x
4x=-14
x=-14:4
x=-3.5
x<-5<br>-3x-15=1-x
-2x=14
x=-7