How do you solve x2+5x+7=0 using the quadratic formula?

3 Answers
Somebody N.
Mar 22, 2018

−5+i√32 and −5−i√32

Explanation:

For quadratic equations of the form:

ax2+bx+c

The quadratic formula is given by:

−b±√b2−4ac2a

From given equation we have:

a=1

b=5

c=7

Putting these values in the quadratic formula:

−(5)±√(5)2−4(1)(7)2(1)=−5±√25−(28)2

=−5±√−32

We can write this in the following way:

√−3=√3×−1=√3⋅√−1

If √−1=i

Then:

−5+i√32 and −5−i√32

These are known as complex roots.

Shwetank Mauria
Mar 22, 2018

x=−5+i√32 or −5−i√32

Explanation:

Accordng to quadratic formula, solution of quadratic equation ax2+bx+c=0 is

x=−b±√b2−4ac2a

Hence solution of x2+5x+7=0 is

x=−5±√52−4⋅1⋅72

= −5±√25−282

= −5±√−32

i.e. x=−5+i√32 or −5−i√32

Gazza
Mar 22, 2018

No real solutions

Explanation:

x2+5x+7=0

Use the quadratic formula with a=1,b=5,c=7

x=−b±√b2−4ac2a

x=−5±√(5)2−4(1)(7)(2)(1)

x=−5±√25−282

x=−5±√−32

No real solution

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