Question

Which two equations would be most appropriately solved by using the quadratic formula? Select each correct answer. (x+8)(x+9)=0 5x2+7x=15 0.25x2+0.8x−8=0 (x−3)2=36

Answer 1

Answer:5x^2 +7x=15

Explanation:

I did test

Answer 2

`5x^(2) +7x =15`

`0.25x^(2) +0.8x-8=0`

Explanation:

Given equations :
`(x+8)(x+9)`

`5x^(2) +7x =15`

`0.25x^(2) +0.8x-8=0`

`(x-3)^(2)=36`

Solution:

A)
`5x^(2) +7x =15`

It is not appropriately solved by using the quadratic formula because the solution is direct

The solution is x=-8 and x=-9

B)
`5x^(2) +7x =15`

⇒
`5x^(2) +7x-15=0`

It is appropriately solved by using the quadratic formula because the solution is not direct

C)
`0.25x^(2) +0.8x-8=0`

It is appropriately solved by using the quadratic formula because the solution is not direct

D)
`(x-3)^(2)=36`

⇒
`(x-3)^(2)=6^2`

⇒
`(x-3)=6`

⇒
`x=6+3`

⇒
`x=9`

It is not appropriately solved by using the quadratic formula because the solution is direct.

Hence Option B and C are the two equations would be most appropriately solved by using the quadratic formula.