Need your help with my daughter math assignment in algebra. how to solve and check the quadratic equation.?

Question

especially the one with the number that does not have a perfect square root. help me solve this equation. x exponent 2 is equal to 81

Answer 1

x² = 81

√x² = ± √81

x = ± 9

- - - - - - s-

Answer 2

WAKE UP AND READ THE QUESTION BEFORE ANSWERING, PEOPLE -- THEY ARE ASKING ABOUT HOW TO SOLVE USING THE QUADRATIC EQ AND HOW TO CHECK THEIR ANSWERS

Okay, your question is not asked too well, but you are asking about the quadratic equation and the formula and x^2 = 81.

Don't worry about the quick answer boys.

Now, lets start by rearranging the equation into standard quadratic form of ax^2 + bx +c =0. (^ means raised to the power of, so ^2 means squared). Now your equation should be x^2 -81 =0. This would make your a, b and c as:

a =1
b=0
c=-81

because the equation can be seen as (1)x^2+(0)x-81=0

Now plug into the quadratic equation

roots = [(-b)(+/-) SQ RT(b^2-4ac)]/2a

roots = [(0)(+/-) SQ RT((0)^2-4(1)*(-81)]/2(1)

roots = (+/-)SQRT(324/2)

roots = (+/-)SQRT(162)

Ok, did you get to this point? I assume so, because you talk about no perfect square. That's a whole different question. Congrats for getting this far. I don't think I actually did the equation right and it has been years since i have used this, but this is where the checking taht you asked about comes in. When you are done, you should be able to plug your answers back into the original equation and it should balance. For example, plug my bad answer back into your original equation x^2 =81 so (sqrt(162))^2 should equal 81, but it doesn't so you know you made a mistake like me. The answer is obviously +/-9 but I'm sure your teacher wants you to work it out in the quadratic form.

Ok, and now that i found out my answer is wrong, by checking, my mistake my be that the sqrt sign should only cover the stuff on the numerator, so the equation should have been:

roots = [(0)(+/-) SQ RT((0)^2-4(1)*(-81)]/2(1)

roots = (+/-)sqrt(324)/2 = [sqrt(81)*sqrt(4)]/2

roots = (+/-)[(9*2)/2

roots = (+/-) 9

Another way to check you answers, are to plug them into these other formulas.

(Root One) + (Root Two) = - (b/a)

and

(Root One) * (Root Two) = (c/a)

Plug 9 and -9 into these equations as a check. I'm not sure which way your teacher told you to check, but the first way is better, plug your roots back into you original formula to check.

Hope this helps and good luck.

Answer 3

x^2 = 81
=> x^2 -- 81 = 0
=> x^2 -- 9^2 = 0
=> (x + 9)(x -- 9) = 0
=> x + 9 = 0 or x -- 9 = 0
=> x = -- 9 or x = 9

Answer 4

Daawg - I dont do maths frequently yet when I do i understand what im doin ya dig? dat different youthful blood needs you to do the quadratic employer yet dat aint in any respect nessessary via fact they isn't a 2nd x term in yo equation ya dig? x^2 is x squared ok dawg? 19ca14e7ea6328a42eeb13d585e4c22x^2 = 108 x^2 = 19ca14e7ea6328a42eeb13d585e4c2219ca14e7ea6328a42eeb13d585e4c22 x = ± ?[19ca14e7ea6328a42eeb13d585e4c2219ca14e7ea6328a42eeb13d585e4c22] x = ±36 x = 36, -36 the ± image skill this is the two effective or detrimental son. this is sensible becuz in case you sq. -36 ya git 19ca14e7ea6328a42eeb13d585e4c2219ca14e7ea6328a42eeb13d585e4c22, and if ya sq. 36 ya git 19ca14e7ea6328a42eeb13d585e4c2219ca14e7ea6328a42eeb13d585e4c22. the two artwork ya dig?

Answer 5

Hi,

x² = 81

so x = ±9

As it turns out, 81 is indeed a perfect square. Now, why ±9?
Because

9 X 9 = 81

and

-9 X -9 = 81

As it turns out, every square root of x has 2 roots, every cube root of x has 3 roots, every fourth root of x has 4 roots, and so on. This is in accordance with the Fundamental Theorem of Algebra.

I fear I may have swamped you with information you weren't looking for. If so, please accept my apologies.

James :-)

Answer 6

firstly get an education, secondly whats the quadratic equation, you mean x^2=81? , x=-9/9 that is a perfect square so i dont know what your on about

Answer 7

x^2 = 81
x^2 = 9^2
Therefore, x=9

Answer 8

x^2 = 81
x = ±√81
x = ±9

then
x1 = +9
x2 = -9

Since: (+9)² = 81 and (-9)² = 81

Bye and good luck !!