<span>x^2-12x+45=(x-15)(x+3)</span>
<span>x^2-12x+45-(x^2-12x-45)=0</span>
<span>x^2-12x+45-x^2+12x+45=0</span>
<span>-12x+45+12x+45=0</span>
<span>45+45=0</span>
<span>900
</span>
56-38-27+42=33
-45-31-20+19=19-45-31-20=-77
а что подчеркнуть я не понял
1) x^2 + 0,8x + 0,16 - 4x^2 = 0
(x + 0,4)^2 - (2x)^2 = 0
(x + 0,4 - 2x)(x + 0,4 + 2x) = 0
(0,4 - x)(3x + 0,4) = 0
x1 = 0,4; x2 = -0,4/3 = -2/15
2) 4x^2 - 11x = 0
x(4x - 11) = 0
x1 = 0; x2 = 11/4
3) 2x(x - 8)^2 - x^2*(x - 8) = 0
x(x - 8)(2(x - 8) - x) = x(x - 8)(2x - 16 - x) = x(x - 8)(x - 16) = 0
x1 = 0; x2 = 8; x3 = 16