(2-0,5)²-0.5(0.5+4)=2.25-2.25=0
=-1/(1+x²) _________________________________
1.5x(3x2-5)(2x2+3)= 1.5x(6x4+9x2-10x2-15)= 9x4+13.5x2-15x2-22.5= 9x4-1.5x2-22.5
(100x-2(7x-2y))(100x+2(7x-2y)=(86x-4y)(114x-4y),
а можно так:100x^2-4(49x^2-28x+4y^2)=100x^2-(196-112x+16y^2)=
=100x^2-(14x-4y)^2=(100x-14x+4y)(100x+14x-4y)=(86x+4y)(114x-4y)
По второй=)
А в первой формуле не синус должен быть, а косинус)
cos <var>2</var><span>α </span><em>=</em><span> </span><var>2 </var><span>· </span>cos<var>2 </var><span>α </span><em>− </em><var>1</var>