The only solution of the equation x2 + bx + 16 = 0 is x = 4. What is the value of b?

b = –16
b = –8
b = 8
b = 16

Question

The only solution of the equation x2 + bx + 16 = 0 is x = 4. What is the value of b?

b = –16
b = –8
b = 8
b = 16

Extrinix · Answer

If $\sf{x=4}$, then we can just plug that in and solve for $\sf{b}$.

$\sf{4^2 + 4(b) + 16 = 0}$

Simplify by multiplying the power
$\sf{16 + 4(b) + 16 = 0}$

Next, combine like terms.
$\sf{4(b) + 32 = 0}$

After that, we subtract 32 from both sides.
$\sf{4(b) = -32}$

Then, divide both sides by $\sf{4}$, and you’ll have your answer.

Extrinix · Answer

@surjithayer wrote:

x=4 x-4=0 squaring $$(x-4)^2=0$$ $$x^2-8x+16=0$$ compare with $$x^2+bx+16=0$$ b=-8

Will you please, for the love of everything, stop just answering questions that have already been answered.