=7/(x-y)(x+y) +5/x(x-y) -12/x(x+y) =(7x+5(x+y) -12(x-y)) /x(x-y)(x+y) =(7x+5x+5y -12x +12y) /x(x-y)(x+y) =17y /x(x²-y²)
ответ: 17y /x(x²-y²)
N(n+1)/2 число матчей n-число команд
(n+1)(n+2)/2 новой число матчей
n(n+1)/2*1,2=(n+1)/n+2)/2
n*1,2=n+2
n+n/5=n+2
n/2=2
n=10
первоначально 10 команд
Расписываю всё подробно:
а) 8-(2+a)(3a+4) = (2+a)(3a+4) = 2*3a+2*4*a*3a+a*4 = 6a+2*4+3aa+4a = 6a+8+3aa+4a = 6a+8+3a²+4a = 3a²+6a+4a+8 = 3a²+10a+8 = -(3a²+10a+8)=-(3a²)-(10a)-(8) = -3a²-10a-8 = -3a²-10a+8-8 = -3a²-10a
б) 2a³+(a+a²)(5-2a) = (a+a²)(5-2a) = a*5+a(-2a)+a²*5+a²(-2a) = a*5-a*2a+a²*5-a²*2a = 5a-2a²+5a²-2a²a = 5a-2a²+5a²-2a³ = 5a+3a³-2a³ = 2a³+5a+3a²-2a³ = 3a²+5a
в) (1-x)(2+2x)+(2-x)(1-2x) = (1-x)(2+2x) = 1*2+1*2x-x*2-x*2x = 2+2x-2x-2xx = 2+2x-2x-2x² = 2-2x² = 2-2x²+(2-x)(1-2x) = 2*1+2(-2x)-x*1-x(-2x) = 2*1-2*2x-x*1+x*2x = 2-4x-x+2x² = 2-5x+2x² = 2-2x²+2-5x+2x² = -2x²+2x²-5x+2+2 = -5x+2+2 = -5x+4
г) (x-2)(x-5)-(x-3)(x-4) = (x-2)(x-5) = x*x+x(-5)-2*x-2(-5) = xx*x*5-2x+2*5 = xx-7x+2*5 = x²-7x+2*5 = x²-7x+10 = x²-7x+10-(x-3)(x-4) = (x-3)(x-4) = x*x+x(-4)-3*x-3(-4) = xx-x*4-3x+3*4 = xx-x*4-3x+3*4 = xx-7x+3*4 = x²-7x+3*4 = x²-7x+12 = -(x²-7x+12) = -(x²)-(-7x)-(12) = -x²+7x-12 = x²-7x+10-x²+7x-12 = x²-x²-7x+7x+10-12 = x²-x²+10-12 = 10-12 = -2
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а) 3(x-4)+x²-4x = 3x-12+x²-4x = x²-x-12 = (x+3)(x-4)
б) 2x-8-x(x-4) = 2x-8-x²+4x = -x²+6-8 = -(x-2)(x-4)
в) x³+5x²-2x-10 = x²(x-5)-2(x+5) =(x+5)(x²-2) = (x+5)(x+√2)(x-√2)
г) x³-6x²-2x+12 = x²(x-6)-2(x-6) = (x-6)(x²-2) = (x-6)(x+√2)(x-√2)
3x²-7x+2
2-6x
10x+2
2-6x = 5x²
3
5x²=3
x²=3:5=0.6
x²=0.6•2=1.2
9,4-8,2+0,6-2,8
1)9,4-8,2=1,2
2)1,2+0,6=1,8
3)1,8-2,8= -1
Ответ: -1