SOLUTION: x^2+3x-40=0

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Question 188290This question is from textbook
: x^2+3x-40=0 This question is from textbook

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2%2B3x-40=0 Start with the given equation.


Notice we have a quadratic equation in the form of ax%5E2%2Bbx%2Bc where a=1, b=3, and c=-40


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-%283%29+%2B-+sqrt%28+%283%29%5E2-4%281%29%28-40%29+%29%29%2F%282%281%29%29 Plug in a=1, b=3, and c=-40


x+=+%28-3+%2B-+sqrt%28+9-4%281%29%28-40%29+%29%29%2F%282%281%29%29 Square 3 to get 9.


x+=+%28-3+%2B-+sqrt%28+9--160+%29%29%2F%282%281%29%29 Multiply 4%281%29%28-40%29 to get -160


x+=+%28-3+%2B-+sqrt%28+9%2B160+%29%29%2F%282%281%29%29 Rewrite sqrt%289--160%29 as sqrt%289%2B160%29


x+=+%28-3+%2B-+sqrt%28+169+%29%29%2F%282%281%29%29 Add 9 to 160 to get 169


x+=+%28-3+%2B-+sqrt%28+169+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%28-3+%2B-+13%29%2F%282%29 Take the square root of 169 to get 13.


x+=+%28-3+%2B+13%29%2F%282%29 or x+=+%28-3+-+13%29%2F%282%29 Break up the expression.


x+=+%2810%29%2F%282%29 or x+=++%28-16%29%2F%282%29 Combine like terms.


x+=+5 or x+=+-8 Simplify.


So the answers are x+=+5 or x+=+-8