1)
(x-5)²-7 = x²-10x+25-7 = x²-10x+18
2)
(4m+3n)²+(2m-6n)²= 16m²+24mn+9n²+4m²-24mn+36n² = 20m²+45n²
3)
X(x-2)-(x-3)² = x²-2x-(x²-6x+9) = x²-2x-x²+6x-9 = 4x-9
Объяснение:
x+x-y = 23
2x-y = 23
<u><em>y = 2x-23</em></u>
<u />
x+y+y = 54
x+2y = 54
<u><em>2y = 54-x</em></u>
<u />
y-z-z = 7
y-2z = 7
<u><em>y = 7+2z</em></u>
<u><em /></u>
2x-23 = 7+2z
2x = 7+2z+23
2x = 2z+30
x = (2z+30):2
<u><em>x = z+15</em></u>
<u><em /></u>
2y = 54-x
2y = 54-(z+15)
2y = 54 - z - 15
2y = 39-z
<u><em>y = (39-z):2</em></u>
<u><em /></u>
y = y
(39-z):2 = 7+2z
39-z = 2(7+2z)
39-z = 14+4z
-z-4z = 14 - 39
-5z = -25
<u><em>z = 5</em></u>
<u><em>y = 7+2z = 7+2*5 = 17</em></u>
<u><em>x = z+15 = 5+15 = 20</em></u>
y+x*z-z = 17+20*5-5 = 17+100-5 = <u>112</u>
<u />
<h3>Ответ: 112.</h3>
Если не ошибаюсь, то нужно 900:6=150 литров за час
Положительные: -6х+12>0
6x<12
x<2
отрицательные: -6х+12<0
6x>12
x>2