Как то так .................
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]
1.а)-63xy5/81xy4=-7/2y=-3,5y
Б)5a-20c/15ac=5(a-4c)/15ac=a-4c/3ac
В)a2-9/15+5a=(a-3)(a+3)/5(3+a)=a-3/5
Г)b2+6b+9/b2-9=b-3/(b-3)(b+3)=1/b+3