SOLUTION: I actually have 2 questions and i am really having problems. i have tried the first one but it does not look right. and the second is a word problem one and i cant not even figur

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: I actually have 2 questions and i am really having problems. i have tried the first one but it does not look right. and the second is a word problem one and i cant not even figur      Log On


   

Question 476930: I actually have 2 questions and i am really having problems. i have tried the first one but it does not look right. and the second is a word problem one and i cant not even figure out how to do this one.
for the randicand i am using the capital V

1. solve: 15x^2 + 7t = 2
put to standard: 15x^2 +7t - 2 =0
a=15 b=7 c= -2
x= -7+- V7^2 - 4(15)(-2)/2 * 15
x= -7+- V49-120/30

x = 1/6 or x = 0.3



the second one ( word prob.)
Abby rows 10 km upstream and 10 km back in a total of 3 hr. the speed of the river is 5 km/h. find abbys speed in still water.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Please post questions one at a time. I'll do the first one to get you started.

# 1




15x%5E2%2B7x=2 Start with the given equation.


15x%5E2%2B7x-2=0 Get every term to the left side.


Notice that the quadratic 15x%5E2%2B7x-2 is in the form of Ax%5E2%2BBx%2BC where A=15, B=7, and C=-2


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


x+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29 Start with the quadratic formula


x+=+%28-%287%29+%2B-+sqrt%28+%287%29%5E2-4%2815%29%28-2%29+%29%29%2F%282%2815%29%29 Plug in A=15, B=7, and C=-2


x+=+%28-7+%2B-+sqrt%28+49-4%2815%29%28-2%29+%29%29%2F%282%2815%29%29 Square 7 to get 49.


x+=+%28-7+%2B-+sqrt%28+49--120+%29%29%2F%282%2815%29%29 Multiply 4%2815%29%28-2%29 to get -120


x+=+%28-7+%2B-+sqrt%28+49%2B120+%29%29%2F%282%2815%29%29 Rewrite sqrt%2849--120%29 as sqrt%2849%2B120%29


x+=+%28-7+%2B-+sqrt%28+169+%29%29%2F%282%2815%29%29 Add 49 to 120 to get 169


x+=+%28-7+%2B-+sqrt%28+169+%29%29%2F%2830%29 Multiply 2 and 15 to get 30.


x+=+%28-7+%2B-+13%29%2F%2830%29 Take the square root of 169 to get 13.


x+=+%28-7+%2B+13%29%2F%2830%29 or x+=+%28-7+-+13%29%2F%2830%29 Break up the expression.


x+=+%286%29%2F%2830%29 or x+=++%28-20%29%2F%2830%29 Combine like terms.


x+=+1%2F5 or x+=+-2%2F3 Simplify.


So the solutions are x+=+1%2F5 or x+=+-2%2F3