1)
1/7*(0,14+2,1-3,5) =
= 1/7 * (14/100 + 21/10 - 35/10) =
= 1/7 * 14/100 + 1/7 * 21/10 - 1/7 * 35/10 =
= 1/50 + 3/10 - 5/10 = 1/50 + 15/50 - 25/50 = -9/50 (или -0,18),
2)
1/12*(4,8-0,24-1,2) =
= 1/12*(48/10 - 24/100 - 12/10) =
= 1/12 * 48/10 - 1/12 * 24/100 - 1/12 * 12/10 =
= 4/10 - 1/50 - 1/10 = 20/50 - 1/50 - 5/50 = 14/50 = 7/25 (или 0,28),
3)
(18 6/7 + 21 3/4) : 3 =
= ((18 + 21) + (6/7 + 3/4)) : 3 =
= (39 + (24/28 + 21/28)) : 3 =
= (39 + 45/28) : 3 = 39 : 3 + 45/28 : 3 =
= 13 + 45/28 * 1/3 = 13 + 15/28 = 13 15/28,
4)
(15 5/7 + 20 15/16 ) * 1/5 =
= ((15 + 20) + (5/7 + 15/16)) * 1/5 =
= (35 + (80/112 + 105/112)) * 1/5 =
= (35 + 185/112) * 1/5 = 35 * 1/5 + 185/112 * 1/5 =
= 7 + 37/112 = 7 37/112
Объяснение:
1)
a) x² - 6x + 5 = 0;
D = 16;
X1 = 5;
X2 = 1;
ответ: 5, 1
б) x² - 5x = 0;
x (x - 5) = 0;
X = 0 или x = 5;
ответ: 0, 5
в) 6x + x²- 7 = 0
x² + 6x - 7 = 0
D=6²-4*1*7=36-28=√8=2√2
x1 = -2√2
x2 = -4√2
ответ: -2√2, -4√2
г) 3x² - 48 = 0
3 (x² - 16) = 0
(x - 4) (x + 4) = 0
x1 = 4
x2 = -4
ответ: 4, -4
2)
S = x (x - 6) = 40
x² - 6x - 40=0
D = 36 + 160 = 196 = 14²
x₁ = (6 + 14) / 2 = 10
x₂ = (6 - 14) / 2 = -4
Длина = 10
Ширина = 10 - 6 = 4
3)
х² + рх - 18 = 0
81 - 9p - 18 = 0
-9p = -63
p = 7
x² + 7x - 18 = 0
x₁ = -9 x₂ = 2
4)
х1 + х2 = -b;
x1 * x2 = c
9 - 4 = 5 b = -5
9 * (-4) = 36 c = -36
х² - 5х - 36 = 0