1)15x²+8x+1=15(x+1/3)(x+1/5)
D=64-60=4
x1=(-8-2)/30=-1/3
x2=(-8+2)/30=-1/5)
20x²-31x+12=20(x-3/4)(x-4/5)
D=961-960=1
x1=(31-1)/40=3/4
x2=(31+1)/40=4/5
(15x²+8x+1)/(20x²-31x+12)≤0
+ _ + _ +
-------------[-1/3]-------[-1/5]-----(3/4)----------(4/5)----------
x∈[-1/3;-1/5] U 93/4;4/5)
2){2x-x>8-2⇒x>6
{x²-2x-63≥0⇒x≤-7 U x≥9
x1+x2=2 U x1*x2=-63⇒x1=-7 U x2=9
x∈[9;∞)
100-81x²=0
(10-9x)(10+9x)=0
10-9x=0 10+9x=0
-9x=-10 9x=-10
x=10/9 x=-10/9
12x⁵-3x³=0
3x³(4x²-1)=0
3x³(2x-1)(2x+1)
x=0 2x-1=0 2x+1=0
2x=1 2x=-1
x=1/2 x=-1/2
Решение задания приложено