![\frac{-15}{(x+1)^2-3} \geq 0](https://tex.z-dn.net/?f=+%5Cfrac%7B-15%7D%7B%28x%2B1%29%5E2-3%7D++%5Cgeq+0)
Так как числитель (-15)<0, то вся дробь будет неотрицательной, если знаменатель меньше 0 :
![(x+1)^2-3< 0\\\\(x+1)^2-(\sqrt3)^2<0\\\\(x+1-\sqrt3)(x+1+\sqrt3)<0\\\\+++(1-\sqrt3)---(1+\sqrt3)+++\\\\x\in (1-\sqrt3;1+\sqrt3)](https://tex.z-dn.net/?f=%28x%2B1%29%5E2-3%3C+0%5C%5C%5C%5C%28x%2B1%29%5E2-%28%5Csqrt3%29%5E2%3C0%5C%5C%5C%5C%28x%2B1-%5Csqrt3%29%28x%2B1%2B%5Csqrt3%29%3C0%5C%5C%5C%5C%2B%2B%2B%281-%5Csqrt3%29---%281%2B%5Csqrt3%29%2B%2B%2B%5C%5C%5C%5Cx%5Cin+%281-%5Csqrt3%3B1%2B%5Csqrt3%29)
2)a)(7m-n)(7m+n)/-3mn(7m-n)=-(7m+n)3mn
b)(9x-4)(9x+4)/(9x+4)^2=(9x-4)/(9x+4)
3)(x-4)^2-25=(x-4)^2-5^2=(x-4-5)(x-4+5)=(x-9)(x+1)=0
1)x-9=0 2) x+1=0
x=9 x=-1
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<span>8,4х+3-5(7,2х+0,3) = 8,4х+3 -36х -1,5= -27,6х +1,5</span>
<span>при х = 2/3</span>
<span>-27,6 х 2/3 +1,5 = -27 6/10 х 2/3 + 1 5/10= - 27 3/5 х 2/3 +1 1/2= -138/5 х 2/3 +3/2= -92/5 +3/2 = (-184 +15)/10 = -169/10= -16,9</span>