4x(4x^2-10x+7)+3x(4x^2-8x+7)=(4x^2-8x+7)(4x^2-10x+7)
16x^3-40x^2+28x+12x^3-24x^2+21x=16x^4-40x^3+28x^2-32x^3+80x^2-56x+28x^2-70x+49
28x^3-64x^2+49x=16x^4-72x^3+136x^2-126x+49
100x^3-200x^2+175x-49-16x^4=0
-16x^4+100x^3-200x^2+175x-49=0/-1
16x^4-100x^3+200x^2-175x+49=0
(2x-7)(2x-1)(4x^2-9x+7)=0
1)2x-7=0
2x=7
x=7/2
2)2x-1=0
2x=1
x=1/2
3)4x^2-9x+7=0
d=81-112=-31<0
Ответ:( 7/2:1/2)
Сумма корней: 7/2+1/2=8/2=4
<span>(n^2-n-1)(n^2-n+1)</span>=n^4-n^3+n^2-n^3+n^2-n-n^2+n-1=n^4-2n^3+n^2-1
а₁ = 8
а₁₂ = 29
Найти S₁₅
1)
a₁₂ = a₁+ 11d
29 = 8 + 11d
11d = 21;
d = 21/11
2)
a₁₅ = a₁ + 14d
а₁₅ = 8 + 14*21/11= (88+294)/11 = 382/11
3)
S₁₅ = (a₁+a₁₅) * 15/2
S₁₅ = (8+382/11) * 15/2 = 470/11*15/2= 3525/11=320 5/11
Ответ: 320 ⁵/₁₁
42/(3+4) * 4= 24 (га) - занимают технические культуры