A) 3x(a+b) + (a+b).1=(a+b)(3x+1)
B) 2a(m-n) - (m-n).1 = (m-n)(2a-1)
C)4y(c+d) - (c+d).1= (c+d)(4y-1)
неравенство пишется слитно.
4x^2 + 10x - 20 <= (x+2)^2
4x^2 + 10x - 20 - x^2 - 4x - 4 <=0
3x^2 + 6x - 24 <=0
x^2 + 2x - 8<=0
D1 = 1 + 8 = 9
x1 = -1 -3 = -4
x2 = -1 + 3 = 2
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---------[-4]------------------------[2]------------->x
+ - +
ответ: [-4;2]
<span> c=(</span><em /><span>a+b)/2, геометрическое c=√ab</span>