1.

Evaluate `lim_(x rarr oo) (3x^(2)+4x+5)/(4x^(2)+7)`.

Answer» Put `x = (1)/(y), "when" x rarr oo, y rarr 0`
`therefore underset(x rarr oo)("lim")(3x^(2)+4x+5)/(4x^(2)+7)=underset(y rarr 0)("lim")(3*(1)/(y^(2))+4*(1)/(y)+5)/(4*(1)/(y^(2))+7)`
`" "=underset(y rarr 0)("lim")(3+4y+5y^(2))/(4+7y^(2))=(3+0+0)/(4+7(0))=(3)/(4)`.


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