Ответ:
Объяснение:cos2x-3cosx+2=0;
2cos²x-1-3cosx+2=0;
2cos²x-3cosx+1=0;( кв. ур-ие отн-но cosx) D=9-8=1
cosx=1/2⇔x=±π/3+2πn,n∈z
или cosx=1-- x=2πn,n∈z
Ответ:
Объяснение:
1.
a) 39x³y/26x²y²=1,5x/y
b)
5y/(y²-2y)= 5y/((y(y-2))= 5/(y-2)
c)
(3a-3b)/(a²-b²)= 3(a-b)/(a-b)(a+b)=3/(a+b)
2.
a)
(3-2a)/2a - (1-a²/a ) = [a(3-2a)-2(1-a²)]/2a² = (3a-6a²-2+2a²)/2a²=
=(-4a²+3a-2)/2a²
b)
1/(3x+y) - 1/(3x-y) =[3x-y-(3x+y)/(9x²-y²)= (3x-y-3x-y)/(9x²-y²)=
=-2y/(9x²-y²)
c)
(4-3b)/(b²-2b) +3/(b-2)= (4-3b)/b(b-2) + 3/(b-2)=(4-3b+3b)/b(b-2)=
=4/(b²-2b)
<span>а) (х - 3)(х + 3) - х(х - 5) = х</span>² - 3² - х² + 5х = -9 + 5х = 5х - 9
<span>б) (m - 5)</span>² <span>- (m - 4)(m + 4) = m</span>² - 10m + 25 - (m² - 16) = m<span>² - 10m + 25 - m² + 16 =
= -10m + 41</span>
(x+6)=(x-4)(x+4)-8
x+6=x^2-16-8
x^2-16-8-x-6=0
x^2-x-30=0
По Th Виетта:
x1=-5
x2=6
сложение Z1+Z2=(3+4i)+(3-4i)=(3+3)+(4-4)i=6+0i=6