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
_ + _
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0 6
x∈
7)x=0,5 x=-0,8 x=1
_ + _ +
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-0,8 0,5 1
x∈(-≈;-0,8] U [0,5;1]
-9.5-(-10.2)=0.7
-10.5+0,7(n-1)>0
-10.5+0.7n-0.7=0,7n-11.2>0
n>11.2/0.7=16
-10,2+0,7*15=0,3
12,5-11,2=1,3
12,5-1,3(n-1)<0
12,5-1,3n+1,3<0
13,8<1,3n
n>13,8/1.3=11
12,5-1.3*10=-0,5