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Can the limit be found without using L'hospital rule?
lim x --> 1
[ √(x) - x² ] ÷ [ 1 - √(x) ]
Is it possible to solve this limit without using L'hospital rule, since it hasn't been taught in class yet?
Thank you
4 Answers
- Geeganage WLv 52 years agoFavorite Answer
lim x --> 1, [ √(x) - x² ] ÷ [ 1 - √(x) ] = lim x --> 1, [ √(x) - x² ] [ 1 + √(x) ]÷ [ 1 - √(x) ][ 1 + √(x) ]
= lim x --> 1,√(x) [ 1 - x√(x)] [ 1 + √(x) ]÷ (1 - x) = lim x --> 1, √(x) [ 1+ √(x) -x√(x) - x²] /(1-x)
=lim x --> 1,√(x){(1-x)(1+x)+(1-x)√(x)}/(1-x) = lim x --> 1,√(x){(1+x)+√(x)} =√(1){(1+1)+√(1)} = 3
- Anonymous2 years ago
u = √x
[ √(x) - x² ] ÷ [ 1 - √(x) ]
= (u - u⁴)/(1-u)
=[u(1 –u)(1 + u + u²)]/(1 –u)
=u(1 + u + u²) (u ≠ 1)
Lim (u → 1)[ u(1 + u + u²)] =2(1 + 1 + 1) = 3.
[u → 1 as x → 1].
- King LeoLv 72 years ago
.
[ √(x) - x² ] / [ 1 - √(x) ]
let t = √x
∴ x = t²
[ √(x) - x² ] / [ 1 - √(x) ]
= ( t - (t²)² ) / ( 1 - t )
= ( t - t⁴ ) / ( 1 - t )
= t ( 1 - t³ ) / ( 1 - t ) but difference of cubes (1 - t³ ) = ( 1 - t )( 1 + t + t² )
= t ( 1 - t )( 1 + t + t² ) / ( 1 - t ) cancel out the 1 - t
= t ( 1 + t + t² )
= √x ( 1 + √x + x )
∴
lim x➝1 { √x ( 1 + √x + x ) }
= √1 ( 1 + √1 + 1 )
= 3
- 2 years ago
Let sqrt(x) = u
(u - u^4) / (1 - u) =>
u * (1 - u^3) / (1 - u) =>
u * (1 - u) * (1 + u + u^2) / (1 - u) =>
u * (1 + u + u^2) =>
sqrt(x) * (1 + sqrt(x) + x)
x goes to 1
sqrt(1) * (1 + sqrt(1) + 1) =>
1 * (1 + 1 + 1) =>
3