1.
a)D=(-1)^2-4*(1)*(-20)=81
x1=5
x2=-4
b)3x-2x+7=3*(1-x)
3x-2x+7=3*1-3x
7+x=3*1-3x
x=-4-3x
4x=-4
x=-1
( X^2 + 12X + 36 ) - ( X^2 - 25 ) = 79
X^2 + 12X + 36 - X^2 + 25 = 79
12X + 61 = 79
12X = 79 - 61
12X = 18
X = 18 : 12
X = 1.5
ОТВЕТ: Х = 1.5
2sinxcosx +√2cosx =0; cosx( 2sinx+√2) =0; cosx = 0 ; x = π/2 +πn, n∈Z;
2sinx = - √2; sinx = - √2/2; x = [tex] (- 1 ) ^{n+1} π/4 +πn,n∈Z;