(2x-3y)y+(2y-3x)x = 2xy-3y^2+2xy - 3x^2 = 4xy - 3*(x^2+y^2) = 4*(-5) -3*(x^2+y^2) = -20-3*131 = -413<span>
xy = -5
x+y = -11
=> (x+y)^2 = 121
x^2 + 2xy+y^2 = 121
x^2+y^2 = 121-2xy = 121-2*(-5) = 121+10 = 131</span>
I. a) (x-3)²=х²-6x+9
b) (4a-b)(4a+b)=16a²-b²
v) (2y+5)²=4y²+20y+25
г) (х²-1)(х²+1)=x^4-1
значок ^ обозначает в степени
2. a) c²-0.25=(c-0.5)(c+0.5)
b) х²-8x+16=(x-4)²
3. (x+4)²-(x-2)(x+2)=х²+8x+16-х²+4=8x+20=
=8*0.125+20=21
4. a) 2(3x-2y)(3x+2y)=
=2(9х²-4y²)=18х²-8y²
b) (a-5)²-(a+5)²= a²-10a+25-a²-10a-25= -20a
v) (a^3+b²)²=a^6+b^4
5. 9y²-25=0
(3y-5)(3y+5)=0
3y=5, y=5/3=1 2/3
3y= -5, y= -1 2/3(одна целая две третьих)
<span>y^2-2y+5 = ( y - 1 )^2 + 4
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( y - 1 )^2 </span>≥ 0
4 > 0