Question

7-
8-
9-
10-
11-
12-
дам 72 бала

Answer 1

7в , 8г , 9в , 10б , 11б 

$7); a^3-4a=a(a^2-4)=a(a-2)(a+2)\\8); x+(x+6)=54; ,; 2x=48; ,; x=24; ,; x+6=30\\9); 5x-8y=80; ,; x=0; ; Rightarrow ; ; y=-10; Rightarrow ; (0,-10)\\10); left { {{x-3y=1, |cdot (-7)} atop {7x+6y=88}} right. ; left { {{27y=81} atop {x=1+3y}} right. ; left { {{y=3} atop {x=10}} right. ;; ; frac{x}{y}=frac{10}{3}$

$11); -(-a^3b^{-2}c)^4cdot (-2a^{-2}b^4)^3=\\=-(a^{12}b^{-8}c^4)cdot (-2^3a^{-6}b^{12})=8a^6b^4c^4$

12)   1В  ,  2Г  ,  3Б  ,  4А