Помогите с 3 и 4 номером

Question

Помогите с 3 и 4 номером

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Answer 1

3
sin²a=1-cos²a=1-1/2=1/2
12(1+sin²a)=12(1+1/2)=12*3/2=18
4
lim(7x^6-x+1)/(8x^6+x-2)=lin(7-1/x^5+1/x^6)/(8+1/x^5-2/x^6)=
=(7-0+0)/(8+0-0)=7/8

lim(2x²-x-1)/(x²-1)=lin(2x+1)(x-1)/(x+1)(x-1)=lim(2x+1)/x+1)=
=(2+1)/(1+1)=1,5