2tg/1+tg²=2sin/cos : 1+sin²/cos²=2sin/cos : (cos²+sin²)/cos²=2sin/cos*cos²=2sin cos=sin 2a
Помоему так.
12/x+5=-12/5^x
12=-12x
12x=-12
x=-1
<span>(a+b)^2 = a^2+2ab+b^2
</span>16x^2−7x+k = (4x)^2-2*4*k+k^2
2*4*k = 7
8k=7
k=7/8
16x^2−7x+k = 16x^2-7x+49/64 = (4x+7/8)^2
А) 0.5*(-5) + 1,7= -2.5+1.7= -0.8
б) (0.1*47)+(8*0.2) = 4.7+ 1.6= 6.3