Question

помогите пожалуйста))

Answer 1

$frac{a^2-2}{a^2-a-2} =0 \ left { {{a^2-2=0} atop {a^2-2a+a-2 neq 0}} right. \ left { {{a^2=2} atop {a(a-2)+(a-2) neq 0}} right. \ left { {{a=pm sqrt{2} } atop {(a-2)(a+1) neq 0}} right. \ left { {{a=pm sqrt{2} } atop {a neq 2; a neq -1} right. \ a=pm sqrt{2}$
Ответ: $pm sqrt{2}$

$(x-4)^2=25 \ |x-4|=5 \ x-4=5 \ x_1=9 \ x-4=-5 \ x_2=-1$
Ответ: 9 и -1

$frac{1}{1+3 sqrt{5} } + frac{1}{1-3 sqrt{5} } = frac{1-3 sqrt{5}}{(1+3 sqrt{5})(1-3 sqrt{5}) } + frac{1+3 sqrt{5}}{(1-3 sqrt{5})(1+3 sqrt{5}) } = \ = frac{1-3 sqrt{5}+1+3 sqrt{5}}{(1+3 sqrt{5})(1-3 sqrt{5}) } = frac{2}{1-(3 sqrt{5})^2 } = frac{2}{1-45 } = -frac{2}{44 } = -frac{1}{22 }$
Ответ: -1/22

Answer 2

спасибо)