4-5x>=-7
-5x>=-7-4|*(-1)
5x<=11|:5
x<=11/5
вот надеюсь всё понятно :))
<span>ay-12bx+3ax-4by = y(a-4b)+3x(a-4b) = (a-4b)(y+3x)</span>
A = (sin²α -1)/(1-cos²α) = -(1-sin²α)/(1-cos²α) = -cos²α/sin²α = - ctq²α
при α= π/4 получаем
A = - ctq²π/4 = -1.
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<span>(sin^2 a-1)/1-cos^2 a ) !!!</span>