5)x²+6x+9-2x²+8x-49≤0
-x²+14x-40≤0
x²-14x+40≥0
x1+x2=14 U x1*x2=40⇒x1=4 U x2=10
+ _ +
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4 10
х∈(-≈;4] U [10;≈) C
6)-x(x-6)...0
x=0 x=6
_ + _
_______________________________________________
0 6
x∈
7)x=0,5 x=-0,8 x=1
_ + _ +
________________________________________________________
-0,8 0,5 1
x∈(-≈;-0,8] U [0,5;1]