i dont get these math questions?

i need to solve these equations with the quadratic formula?

i really dont get these three can some one plz help, thanks.

1. y= 9-x^2 ( for this one i just need it in the form ax^2 + bx + c)

2. 2x^2 - 3x - 4 = 0

3 x^2 + (x+1)^2 = 25 ( i need this one in the form ax^2 + bx + c)

1 Answer

Relevance
  • 1 decade ago
    Favorite Answer

    1.

    y = 9 - x²

    answer:

    y = -x² + 9

    the bx in this case is still there, but it is zero. this equation is the same as y = -x² + 0x + 9

    I don't think you could really do that with the quadratic formula too efficiently.

    2.

    2x² - 3x - 4 = 0

    just punch this one into the quadratic formula.

    y = ( - b ± √(b² - 4ac)) / 2a

    y = ( - (-3) ± √( (-3)² - 4(2)(-4) )) / 2(2)

    y = ( 3 ± √( 9 - (-32) )) / 4

    y = ( 3 ± √41 ) / 4

    some calculations later, and the answer is:

    y = 2.3507 and y = -0.8507

    3.

    for this one, the first thing you need to do is get everything over to one side.

    x² + (x + 1)² = 25

    x² + (x + 1)² - 25 = 0

    now you expand the (x + 1)²

    how to expand (x + 1)²:

    (x + 1)²

    (x + 1)(x + 1)

    x² + x +x + 1

    x² + 2x + 1

    now let's plug that back into the formula.

    x² + (x + 1)² - 25 = 0

    x² + x² + 2x + 1 - 25 = 0

    now you just combine the like terms.

    x² + x² + 2x + 1 - 25 = 0

    2x² + 2x - 24 = 0

    and there you have it, the answer is 2x² + 2x - 24 = 0

    Hope it helps!

Still have questions? Get your answers by asking now.