Берем производную от <span>2x^2-x
получаем f'(x)= 2*2х-1
f'(x)=0
</span>2*2х-1=0
4x=1
x=1/4
<span>a) 5(x+1.4y)-0.8(2x+y)=5х+7у-1,6х-0,8у=3,4х+6,2
</span><span>б)2/3(x-y-z)-(2/3x-y-z)=2/3х-2/3у-2/3z-2/3x+y+z=1/3y+1/3z=1/3(y+z)
</span><span>в)-a+0.5(3a+0.2b)-(a+0.1b)=-a+1.5a+0.1b-a-0.1b=-0.5a
</span><span>г)-10(2/5b+1/2)+3/4(8-b)+5b=4b-5+6-3/4b=3.25b+1</span>
8-7x=0
-7x=-8
x=8/7 или 1 1/7
(x^2+4-4x)(x^2-4x)+3=0
x^2-4x=t
(t+4)*t+3=0
t^2+4t+3=0
t1=-3 t2=-1
x^2-4x=-1
x^2-4x+1=0
x=2+-√3 x1=2-√3 x2=2+√3
x^2-4x+3=0
x3=1 x4=3
отметь "лучшим"
(ab+1)(a2-b)=a3b-ab2+a2-b