Inequalities 2

Algebra Level 3

Find the smallest value of 4 x ² + 8 x + 13 6 + 6 x \frac{4x²+8x+13}{6+6x} For x≥0


The answer is 2.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Naitik Sanghavi
Aug 7, 2015

4 x ² + 4 x + 4 x + 4 + 9 6 ( 1 + x ) \frac{4x²+4x+4x+4+9}{6(1+x)} = 4 x ( x + 1 ) 6 ( x + 1 ) \frac{4x(x+1)}{6(x+1)} + \frac{4(x+1)}{6(x+1)}+\(\frac{9}{6(x+1)}

So,

2 x 3 \frac{2x}{3} + 2 3 \frac{2}{3} + 3 2 ( x + 1 ) \frac{3}{2(x+1)} = 2 ( x + 1 ) 3 \frac{2(x+1)}{3} + 3 2 ( x + 1 ) \frac{3}{2(x+1)}

Now we have two terms and we need to apply here AM≥GM

Thus by applying this inequality we get the answer as 2 \boxed{2} .

We have:

4 x 2 + 8 x + 13 6 + 6 x = 2 + ( 2 x 1 ) 2 6 x + 6 2 , x 0 \dfrac{4x^2+8x+13}{6+6x}=2+\dfrac{(2x-1)^2}{6x+6}\ge2, \forall x\ge0 .

The equality holds when x = 1 2 x=\dfrac{1}{2} .

So, the answer is 2 \boxed{2}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...