SOLUTION: can you please help me solve this equation 12x^2 + 7 =10 ?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: can you please help me solve this equation 12x^2 + 7 =10 ?      Log On


   



Question 91863This question is from textbook
: can you please help me solve this equation 12x^2 + 7 =10 ? This question is from textbook

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
12x%5E2+%2B+7x+=10 I'm assuming it looks like this right?

12x%5E2+%2B+7x+-10=0 Subtract 10 from both sides


Let's use the quadratic formula to solve for x:


Starting with the general quadratic

ax%5E2%2Bbx%2Bc=0

the general solution using the quadratic equation is:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29

So lets solve 12%2Ax%5E2%2B7%2Ax-10=0 ( notice a=12, b=7, and c=-10)

x+=+%28-7+%2B-+sqrt%28+%287%29%5E2-4%2A12%2A-10+%29%29%2F%282%2A12%29 Plug in a=12, b=7, and c=-10



x+=+%28-7+%2B-+sqrt%28+49-4%2A12%2A-10+%29%29%2F%282%2A12%29 Square 7 to get 49



x+=+%28-7+%2B-+sqrt%28+49%2B480+%29%29%2F%282%2A12%29 Multiply -4%2A-10%2A12 to get 480



x+=+%28-7+%2B-+sqrt%28+529+%29%29%2F%282%2A12%29 Combine like terms in the radicand (everything under the square root)



x+=+%28-7+%2B-+23%29%2F%282%2A12%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)



x+=+%28-7+%2B-+23%29%2F24 Multiply 2 and 12 to get 24

So now the expression breaks down into two parts

x+=+%28-7+%2B+23%29%2F24 or x+=+%28-7+-+23%29%2F24

Lets look at the first part:

x=%28-7+%2B+23%29%2F24

x=16%2F24 Add the terms in the numerator
x=2%2F3 Divide

So one answer is
x=2%2F3



Now lets look at the second part:

x=%28-7+-+23%29%2F24

x=-30%2F24 Subtract the terms in the numerator
x=-5%2F4 Divide

So another answer is
x=-5%2F4

So our solutions are:
x=2%2F3 or x=-5%2F4

Notice when we graph 12%2Ax%5E2%2B7%2Ax-10, we get:

+graph%28+500%2C+500%2C+-15%2C+12%2C+-15%2C+12%2C12%2Ax%5E2%2B7%2Ax%2B-10%29+

and we can see that the roots are x=2%2F3 and x=-5%2F4. This verifies our answer