Author Question: how do you solve these 2 equations using the quadratic formula? (Read 1469 times)

erika

  • Hero Member
  • *****
  • Posts: 522
How do you solve the equation using the quadratic formula?
3x^2 -17=0

or
2y^2=-5y



Thanks for your help !!
Thanks for all the answers. It makes perfect sense now.



xclash

  • Hero Member
  • *****
  • Posts: 681
2y^2+5y=0
y(2y+5=0

y=0 or -5/2

3x^2-17=0
3x^2=17
x^2=17/3
x= sq rt 17/3



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question

sadsdas

  • Newbie
  • *
  • Posts: 10
x= [ -b +/- sqr(b^2 - 4ac) ] / 2a
where:
ax^2 + bx + c = 0

3x^2 -17=0
a= 3
b= 0
c= -17

plug and chug:
x= 2.3805, -2.3805

2y^2=-5y
2y^2 - 5y = 0
a= 2
b= -5
c= 0

plug and chug:
y= 2.5, 0



hummingbird

  • Sr. Member
  • ****
  • Posts: 324
The quadratic formula says:
[-b ± ?(b²-4ab)] / 2a

1)
3x² - 17 = 0

So in this case:
a = 3
b = 0
c = -17

Plug them into the quadratic equation:
[0 ± ?(0 - 4(3)(-17))] / 6

[±?(204)] / 6

[±2?51] / 6

[±?51] / 3 <===Answer




2)
First rearrange the equation:
2y² + 5y = 0

So in this case:
a = 2
b = 5
c = 0

Plug it into the quadratic equation:
[-5 ± ?(25 - 4(2)(0))] / 4

[-5 ± ?25] / 4

[-5 ± 5] / 4

So you have to equations to solve for. I'll do the plus one first:
[-5 + 5] / 4=
0 <===Answer #1

Now the minus one:
[-5 - 5] / 4=
-5/2 <===Answer #2



frankwu

  • Hero Member
  • *****
  • Posts: 549
for 3x^2 - 17 = 0

ax^2 + bx + c = 0

a = 3
b = 0
c = -17

x= (-b(+/-)(b^2-4ac)^1/2)/2a  (quadratic equation)

x = (0(+/-)(0^2-((4)(3)(-17))^1/2)/2*3

x = ((+/-)(204)^1/2)/6

x = (+/-)2*((51)^(1/2))/6

x = pos 2/6 * sqrt51 and x = neg 2/6 * sqrt51

for 2y^2 = -5y, rearrange to:

2y^2+5y+0= 0

a=2
b=5
c=0

y = (-5(+/-)(5*5-4*2*0)^(1/2))/(2*2)

y = (-5(+/-)(25)^(1/2))/4

y = (-5 + 5)/4 and (-5 -5)/4

y = 0 and -10/4



 

Did you know?

More than one-third of adult Americans are obese. Diseases that kill the largest number of people annually, such as heart disease, cancer, diabetes, stroke, and hypertension, can be attributed to diet.

Did you know?

In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.

Did you know?

A strange skin disease referred to as Morgellons has occurred in the southern United States and in California. Symptoms include slowly healing sores, joint pain, persistent fatigue, and a sensation of things crawling through the skin. Another symptom is strange-looking, threadlike extrusions coming out of the skin.

Did you know?

Automated pill dispensing systems have alarms to alert patients when the correct dosing time has arrived. Most systems work with many varieties of medications, so patients who are taking a variety of drugs can still be in control of their dose regimen.

Did you know?

Vaccines prevent between 2.5 and 4 million deaths every year.

For a complete list of videos, visit our video library