<span>а</span>²<span>+4b</span>²<span>-9c</span>²<span>-4ab=a</span>²-4ab+4b²-9c²=(a-2b)²-9c²=(a-2b-3c)(a-2b+3c).
7z²+35z-z-5=0
7z²+34z-5=0
D/4=(b/2)²-ac=17²+7*5=289+35=324=18²
z1=(-b/2+√D/4)/a=(-17+18)/7=1/7
z2=(-17-18)/7=-35/7=-5
z1=1/7
z2=-5.
Решение
1) (b - b⁻¹/²) / (1 - b⁻¹/²) = (b - 1/b¹/²) / (1 - b¹/²) = (b³/² - 1) / (b¹/² - 1) =
= [(b¹/²)³ - 1] / (b¹/² - 1) = [(b¹/² - 1) * (b + b¹/² + 1)] / (b¹/² - 1) =
= b + b¹/² + 1
2) (b + b⁻¹/²) / (1 + b⁻¹/²) = (b + 1/b¹/²) / (1 + b¹/²) = (b³/² + 1) / (b¹/² + 1) =
= [(b¹/²)³ + 1] / (b¹/² + 1) = [(b¹/² + 1) * (b - b¹/² + 1)] / (b¹/² + 1) =
= b - b¹/² + 1
3) b + b¹/² + 1 - b + b¹/² - 1 = 2*b¹/²
4) 2b¹/² * (b⁻¹/² / 2) + 7 = 1 + 7 = 8
5) 8¹/³ = (2³)¹/³ = 2
6х-8у 6* 2/3 - 8*5/8= 4-5=-1