1)
<=> 5-2x =
5-8 = 2x <=> -3 = 2x <=> x = -3/2 = -1.5
2)
=-2 <=> 3+4x = 0.5^(-2) = (1/2)^-2 = 4
=> 3-4x= 4 <=> 3-4 = 4x <=> -1 = -4x => x=-1/4 = -0.25
Ax²+bx+c=0
x₁+x₂=-b/a
x₁x₂=c/a
5x²-2x-1=0
x₁+x₂=2/5
x₁x₂=-1/5
(x₁+x₂)²=x₁²+x₂²+2x₁x₂=(2/5)²
x₁²+x₂²-2/5=4/25
x₁²+x₂²=14/25
!x₁-x₂!=√(x₁-x₂)²=√(x₁²+x₂²-2x₁x₂)=√(14/25+2/5)=√(24/25)=√24/5
80% - 680 р.
100% - x р.
80/100 = 680/х
80х = 68000
х = 850
1) а) у=8-2х
×+8-2х=7
-х+8=7
-х= -1
х=1
дальше по этому же принципу