That's What I'm Talking About!

Algebra Level 2

x 2 + 4 x + 3 + 2 x + 5 = 0 \large \left| { x }^{ 2 }+4x+3 \right| +2x+5=0

The number of real solutions of the equation above is __________ . \text{\_\_\_\_\_\_\_\_\_\_}.


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

Ram Gautam
Jan 18, 2015

We have, x 2 + 4 x + 3 + 2 x + 5 \left| { x }^{ 2 }+4x+3 \right| +2x+5

Here two cases arise.

  • Case 1:- When,

\Rightarrow x 2 + 4 x + 3 > 0 { x }^{ 2 }+4x+3>0

\Rightarrow x 2 + 4 x + 3 + 2 x + 5 = 0 { x }^{ 2 }+4x+3+2x+5=0

\Rightarrow x 2 + 6 x + 8 = 0 { x }^{ 2 }+6x+8=0

\Rightarrow Hence, x=-2, -4

Here, x=-2 doesn't satisfy x 2 + 4 x + 3 > 0 { x }^{ 2 }+4x+3>0 . So, x=-4 is the only solution for Case 1!

  • Case 2:- When,

\Rightarrow x 2 + 4 x + 3 < 0 { x }^{ 2 }+4x+3<0

\Rightarrow x 2 4 x 3 + 2 x + 5 = 0 -{ x }^{ 2 }-4x-3+2x+5=0

\Rightarrow x 2 2 x + 2 = 0 -{ x }^{ 2 }-2x+2=0

\Rightarrow x 2 + 2 x 2 = 0 { x }^{ 2 }+2x-2=0

\Rightarrow x = 1 + 3 , 1 3 x=-1+\sqrt { 3 } ,-1-\sqrt { 3 }

\Rightarrow Hence, x = ( 1 + 3 ) x=-(1+\sqrt { 3 }) satisfies the given condition, while, x = 1 + 3 x=-1+\sqrt { 3 } doesn't!

  • From Case 1 & Case 2 , we get 2 real roots!
Paola Ramírez
Jan 21, 2015

We have two cases: 1. When x 2 4 x 3 + 2 x + 5 = 0 -x^2-4x-3+2x+5=0

x 2 2 x + 2 = 0 -x^2-2x+2=0

x = 1 ± 3 x=-1 \pm \sqrt{3}

  1. When x 2 + 4 x + 3 + 2 x + 5 = 0 x^2+4x+3+2x+5=0

x 2 + 6 x + 8 = 0 x^2+6x+8=0

x = 2 , 4 x=-2,-4

Sustitute in the original equation only 2 -2 and 1 3 -1-\sqrt{3} are solutions.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...