разложите на множители 1.4x^2-42.5st^2-20st+20s^23.c-27cd^34.ab^3+ac^3Решите

4x^2-4=4(x^2-1)=4(x-1)(x+1)     c-27cd^3=c(1-27d^3)=c(1-3d)(1-3d+9d^2)     ab^3+ac^3=a(b^3+c^3)=a(b+c)(b^2-bc+c^2)      

5(x+2)+7=9(x+2)                         (x-2)(3x+5)=0

5x+10+7=9x+18                        3x^2+5x-6x-10=0

5x-9x=18-10-7                    D=1+120=121     
                                         x1=-1 1/2.     x2=-7
-4x=7

x=-7/4
 

5(х+2)+7=9(х+2)   5х+10+7=9х+18

5х-9х=18-10-7   -4х=1   х=минус одна 4-ая