(t-3)(t+5)=t^2+5t-3t-15=t^2+2t-15
(4х-7)(3х-8)= 12x^2+32x-21x+56=12x^2+11x+56
(b-2)(b^2+3b-4)= b^3+3b^2-4b-2b^2-6b+8=b^3+b^2-10b+8
(x+2y)^2=x^2+2x2y+4y^2
(a+b)×(a-b)= a^2-b^2
№1
1) 7/9 - 2/3 = 7/9 - 6/9 = 1/9
2) 3 - 1 11/24 = 1целая 13/24
3) 1/9 + 1ц.13/24 = 8/72 + 111/72 = 119/72 = 1ц. 47/72
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№2
1) 3 7/30 + 2 11/12 = 5 + (7/30 + 11/12) = 5 + 14/60 + 55/60 = 5ц.69/60 = 6ц.9/60 = 6ц 3/20
2) 8 8/15 - 6 3/20 = 128/15 - 126/20 = 512/60 - 378/60 = 134/60 = 2 4/60 = 2 1/15
Формула 1 + 1/sin²α = ctg²α
ctg²α -1=1/sin²α
sin² α= 1/ (сtg²α-1) = 1/(4-1)=1/3
(3у-2)*(у^2-у+1)
3у^3-3у^3+3у-2у^2+2у-2
3у^3-5у^2+5у-2