<span>c+d+3x(c+d) = с + d + 3хс + 3хd = c(1 + 3x) + d(1 +3х) = (с + d) * (1 + 3х)</span>
2. x²-2x-8=0
D=4+4*8=36
x₁=<u>2-6</u>=-2
2
x₂=<u>2+6</u>=4
2
x₁*x₂=-2*4= -8
Ответ: -8
3. 5(х-6)(х+7)<0
(x-6)(x+7)<0
x=6 x=-7
+ - +
------- -7----------- 6----------
\\\\\\\\\\
x∈(-7; 6)
Ответ: (-7; 6)
4) {2x+15>0
{7x-14>0
{2x>-15
{7x>14
{x>-7.5
{x>2
\\\\\\\\\\\\\\\\\\\\\\\
----- -7.5 ------- 2 ----------
\\\\\\\\\\\\\\\\\\\\\
x>2 или х∈(2; +∞)
X^2+y<3
y-x+3>0
y<3-x^2
y-x+3>0
y<3-x^2
0<y-x+3
0<3-x^2-x+3
3-x^2-x+3>0
x^2-x>0
a=1 b=-1 c=0
D=1-0=1
x1= (1+1)/2=1
x2=(1-1)/2=0
y1=2
y2=3
Вроде бы так.
Cos²a=1: (1+tg²a)=1:(1+25/4)=1:29/4=4/29⇒cosx=+-2/√29
sin²x=1-cos²x=1-4/29=25/29⇒sinx=-+5/√29
1)sinx=-5/√29 U cosx=2/√29
(10 соsa+4 sina+15):(2 sina+5 cosa+3 )=(20/√29-20/√29 +15):(-10/√29+10/√29 +3)=
=15 :3=5
2)sinx=5/√29 U cosx=-2/√29
(10 соsa+4 sina+15):(2 sina+5 cosa+3 )=(-20/√29+20/√29 +15):(10/√29-10/√29 +3)=
=15:3=5