1) (a - b) (a +b) = a^ – b^; 2) (a+b)(a^-ab-b^)=a+b
3) (a - b)(a + ab + b^) = aº – b°;
4) (а+b)^=a^+ 2 ab+b^
5) (a - b)^ = a^ – 2ab +b^.

Question

Алгебра: 1) (a - b) (a +b) = a^ – b^; 2) (a+b)(a^-ab-b^)=a*+b* 3) (a - b)(a + ab + b^) = aº – b°; 4) (а+b)^=a^+ 2 ab+b^ 5) (a - b)^ = a^ – 2ab +b^.​

torgor2017 · Accepted Answer

1) sin a = √2/2; a1 = pi/4+2pi*k; cos a1 = √2/2
a2 = 3pi/4+2pi*k; cos a2 = -√2/2
cos(60 + a1) = cos 60*cos a1 - sin 60*sin a1 =
= 1/2*√2/2 - √3/2*√2/2 = √2/4*(1 - √3) = -√2(√3 - 1)/4
cos(60 + a2) = cos 60*cos a2 - sin 60*sin a2 =
= -1/2*√2/2 - √3/2*√2/2 = -√2/4*(1 + √3) = -√2(√3 + 1)/4

2) sin a = 2/3; cos b = -3/4; a ∈ (pi/2; pi); b ∈ (pi; 3pi/2)
cos a < 0; sin^2 a = 4/9; cos^2 a = 1-4/9 = 5/9; cos a = -√5/3
sin b < 0; cos^2 b = 9/16; sin^2 b = 1-9/16 = 7/16; sin b = -√7/4
sin(a+b) = sin a*cos b + cos a*sin b =
= 2/3*(-3/4) + (-√5/3)(-√7/4) = -6/12 + √35/12 = (√35 - 6)/12
cos(-b) = cos b = -3/4

1) (a - b) (a +b) = a^ – b^; 2) (a+b)(a^-ab-b^)=a*+b*3) (a - b)(a + ab + b^) = aº – b°;4) (а+b)^=a^+ 2 ab+b^5) (a - b)^ = a^ – 2ab +b^.​

MOGZ ответил

1) (a - b) (a +b) = a^ – b^; 2) (a+b)(a^-ab-b^)=a+b
3) (a - b)(a + ab + b^) = aº – b°;
4) (а+b)^=a^+ 2 ab+b^
5) (a - b)^ = a^ – 2ab +b^.