How do you solve 4x2+4x=15 using the quadratic formula?

2 Answers
Apr 11, 2018

x=32,52.

Explanation:

First Of All, Convert the Equation to It's General Form ax2+bx+c=0.

So We have,

×x4x2+4x=15

4x2+4x15=0 [Subtract 15 from both sides.]

So, Comparing the Equation with the General Form, We get,

a=4,b=4,c=15.

So, Let's Find the Discriminat.

D=b24ac=4244(15)=16+240=256

As D>0, we will get two roots which are real and distinct.

Now Use The Quadratic Formula or Sridhar Acharya's Rule (whatever you may call it in your country).

α=b+D2a=4+25624=4+168=32

And β=bD2a=425624=4168=52

So, x=32,52

Hope this helps.

Apr 11, 2018

32 or52

Explanation:

Make the expression equal to zero:

4x2+4x15=0

The quadratic formula is:

x=b±b24ac2a

In our case we substitute:

a=4,b=4,c=15

So that the quadratic formula becomes:

x=4±4244(15)24

=4±16+2408

=4±168

=32or52

We can also solve this by factorising (here you need to guess)

4x2+4x15=0

(2x+5)(2x3)=0

Then make both parenthesis equal to zero to get the same answers:

(2x+5)=0 or (2x3)=0