Х²+ 3х-4 = x²+ 4x - x -4 = x(x+4) + (-x-4) =
= x(x+4) - (x+4) = (x-1)(x+4)
x²-8x+15 = x²- 5x-3x - 5*(-3) =
= (x²-3x) + (-5x - 5(-3))=
= x(x-3) - 5(x-3)= (x-5)(x-3)
x²+8x+12= x²+6x+2x+6*2 =
= (x²+6x) + (2x+6*2) =
=x(x+6) + 2(x+6) =(x+2)(x+6)
<span>5x^2+20xy+20y^2 = 5*(x^2+4xy+4y^2) = 5*(х+2)^2 </span>
1,1+5×1,5-0,7×20=1,1+7,5-14=8,6-14=-5,4
250 / ( x - 40 ) - 270 / x = 2
общий знаменатель x( x - 40 ) = x² - 40x
( 250x - 270( x - 40 ))/ ( x² - 40x ) = 2( x² - 40x )
250x - 270x + 10800 = 2x² - 80x
2x² - 80x + 20x - 10800 = 0
2x² - 60x - 10800 = 0
2( x² - 30x - 5400 ) = 0
D = 900 + 21600 = 22500 ; √ D = 150
x1 = ( 30 + 150 ) : 2 = 90
x2 = ( 30 - 150 ) : 2 = - 60
ОТВЕТ 90 ; - 60