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;∞)
Ответ 3
Пусть b=-6 a=-2
a+b=-2-6=-8
b/2=-6/2=-3
-a=-(-2)=2
b-a=-6-(-2)=-6+2=-4
(a-b)*(a+b)=a^2-b^2 => cos^2 75 - sin^2 75 = 2cos^2 75 - 1 = cos 2*75=cos150= минус корень из трех деленое на 2
А) 4m^5k/18m^3k^4=2m^2/9k<span>^3
b) </span>a-3b/a^2-3ab=<span>a-3b/a(a-3b)=1/a
c)</span><span>4p+4q/p^2-q^2=4(p+q)/(p-q)*(p+q)=4/(p-q)</span>
2-3х+5=0
-3х=-7
х=7/3= 2 1/3
Ответ: 2 1/3