Ответ:
Объяснение:
1) х∈[4;+∞)
2)x∈(-∞;0)∪(0;+∞)
3) y=(-3×3+5)/4=(-9+5)/4=-4/4=-1
7х + 3у= 71
3х- 14 = 2у
...............................
2у = 3х- 14
у= 0.5 * ( 3х- 14) = 1.5х- 7
.........................
7х+ 3у= 71
7х+ 3*( 1.5х- 7) = 71
7х + 4.5х- 21 = 71
11.5х= 92
х = 8
у = 1.5 * 8 - 7 = 12 - 7 = 5
Ответ одна доска весит 8 кг, один кирпич весит 5 кг
<span>1. х²- 4=0</span>
<span> (x-2)(x+2)=0</span>
<span> [- совокупность</span>
<span> [x=2</span>
<span> [x=-2</span>
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<span><span>2. х²-4х+4=0 воспользуемся формулой a²-2ab+b² = (a-b)²</span></span>
<span><span>(x-2)²=0</span></span>
x=2
<span>3. 4х²-х=0</span>
<span>x(4x-1)=0</span>
<span>[x=0 [x=0</span>
<span>[4x=1 [x=1/4</span>
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<span><span>4. х(х-1)-(х-5)²=2</span></span>
x²-x-(x²-10x+25)-2=0
x²-x-x²+10x-25-2 = 0
9x-27 = 0
9x = 27
x = 3
а) 16у²-25= (4y-5)*(4y+5)
<span>б) а²-6ав+9в² = (a-3в)²</span>
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<span><span>в) 25у²-а² = (5y-a)*(5y+a)</span></span>
<span>г)с²+4вс+4в² = (с+2в)²</span>
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