1)sin390⁰-sin(-420⁰)+ctg(2π+π/4)=
=sin(360⁰+30⁰)-sin(-360⁰-60⁰)+ctgπ/4=
=sin30⁰-(-sin60⁰)+1=sin30⁰+sin60⁰+1=1/2+√3/2+1=(3+√3)/2;
2)2cos30⁰·ctg60⁰-sin3π/2=2·(√3/2)·(√3/3)-(-1)=2·3/6+1=2;
1) ( a - 12)^3 - 5^3 = ( a - 12 - 5)(a^2-24a+144+5a-60+25)=(a-17)(a^2-19a+109)
2) ( b + 4)^3 + 4^3 = (b + 4 + 4)(b^2+8b+16 -4b-16+16) =(b + 8)(b^2+4b+16)
3) ( x^2 + 1)^2 - 4x^2 = ( x^2 + 1 - 2x)(x^2 + 1 + 2x)=(x^2-2x+1)(x^2+2x+1)=
= (x - 1)(x- 1)(x+ 1)(x+ 1)
4) (y^2 + 2y)^2 - 1 = (y^2 + 2y - 1)(y^2 + 2y + 1) = (y + 2y - 1)(y + 1)(y + 1)
5) ( 9 - c^2 - 6c)(9 + c^2 + 6c)=( - c^2 - 6c + 9)(c^2 + 6c + 9)
6) (4m - m+ n)(4m + m - n)= (3m + n)(5m - n)
А) 2ab+4b/3a*6a^2/a^2b-4b=2b(a+2)/3a*6a^2/b(a^2-4)=2b(a+2)/1*2a/b*(a-2)(a+2) ( 6a^2 и 3а сокращаем и (a+2) сокращаем)=2b/1*2a/b(a-2)=4a/a-2
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