Question

Which two equations would be most appropriately solved by using the quadratic formula?

Answer 1

Remember that quadratic formula: $x= \frac{-b(+/-) \sqrt{b^{2}-4ac} }{2a}$ is used to solve quadratic equations of the form $ax^{2}+bx+c$.

Four our problem, the first one, $(x-1)^2=4$, is not in the form $ax^{2}+bx+c$. So is not a good idea to use the quadratic formula for this one.

The second one, $0.25x^{2}+0.8x-8=0$, is in the correct form. Notice that in this equation $a=0.25$, $b=0.8$, and $c=-8$. It would be appropriate to use the quadratic formula to solve this one.

The third one, $3x^{2}-4x=15$, can be expressed as: $3x^{2}-4x-15=0$. This equation is also in the correct form. Here $a=3$, $b=-4$, and $c=-15$. It would be appropriate to use the quadratic formula to solve this one.

The fourth one, $(x-6)(x+6)=0$, is not in the form $ax^{2}+bx+c$. So is not a good idea to use the quadratic formula for this one.

We can conclude that you should use the quadratic formula to solve the second and third equations.

Answer 2

Answer: second and third equations, dear.