A-(b+c-d)=a-b-c+d
1) неверное равенство
2) неверное равенство
3) верное равенство
Ответ: 3
А) у = 4х + 9 и у = 6х - 54x + 9 = 6x - 54x - 6x = -5 - 9-2x = -14x = 7y = 4 · 7 + 9 = 37y = 6 · 7 - 5 = 37(7 ; 37) б) y = 16x - 7 и y = 21x + 816x - 7 = 21x + 816x - 21x = 8 + 7-5x = 15x = -3y = 16 · (-3) - 7 = - 48 - 7 = -55y = 21 · (-3) + 8 = - 63 + 8 = -55(-3 ; -55) в) y = 10x - 7 и y=510x - 7 = 510x = 12x = 1,2y = 10 · 1,2 - 7 = 12 - 7 = 5y = 5(1,2 ; 5) г) y = 0,1x и y = 140,1x = 14x = 140y = 0,1 · 140 = 14y = 14<span>(140 ; 14)</span>
1) (2a 2 -3a +1) – (7a 2-a) =2a²-3a+1-7a²+a=-5a²-2a+1
2)3x( 4x2 -x )=12x³-3x²
<span>а). 2ху – 3ху2=xy(2-3y)
</span><span>б). 8в4 + 2в3=2b</span>³(4b+1)
В
(x²-1)/(1-x)(1+x+x²) - x²/(x²+x+1)=(x²-1-x²+x³)/(1-x³)=(x³-1)/(1-x³)=-1
д
a/(a(a+3)+(a-8)/a+(7a²-3a-72)/a(a-3)(a+3)=(a²+3a+a³-9a-8a²+72+7a²-3a-72)/a(a²-9)=
=(a³-9a)/(a³-9a)=1
е
1)1/a+1/b=(b+a)/ab
2)2/(a+b)*(b+a)/ab=2/ab
3)1/a²+1/b²+2/ab=(b²+a²+2ab)/a²b²=(a+b)²/a²b²
4)(a+b)²/a²b² :(a+b)²/a²b²=1
Нет, не верно, т.к.
<span>-(-2,7)=2,7
2,7>0, т.е</span>
<span><span>-(-2,7)>0</span>
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