Question

i am completely stuck can someone please help me.
Solve. 3x2 = –21x – 15
a.7+-3sqrt69/2
b.7+-3sqrt29/2
c.-7+-sqrt29/2
d.-7+-isqrt69/2

Answer 1

@Nurali

Answer 2

@sumi29

Answer 3

Rearrange your equation so everything is on one side of the equals sign, and a 0 on the other.

Answer 4

Having done that, see if there are any common factors to all 3 terms. If there is one, divide it out to make the rest of the problem simpler — it won't change the answer.

Answer 5

ok thanks

Answer 6

what do you get after you do that?

Answer 7

well i was between c and d and i think it is d which is \[-7+i \sqrt{69}/2\]

Answer 8

Let's work through it. What do you have for an equation after doing my suggested steps?

Answer 9

hold on i threw away the paper by accident when cleaning up my work space i have to rewrite it

Answer 10

I'll wait, no problem.

Answer 11

i got \[3x ^{2}+21x+15\]

Answer 12

=0, right?

Now is there a common factor to all 3 of those terms?

Answer 13

yes i forgot to add the =0 to the end

Answer 14

common factor?

Answer 15

so it would be 3 as the common factor

Answer 16

yes. and after we take out the 3, we have?

Answer 17

x^2+7x+5

Answer 18

right. what are the values of a,b,c to put into the quadratic formula?

Answer 19

now im am confused

Answer 20

the quadratic formula says that the solutions to \[ax^2+bx+c=0,~a\ne0\] are given by \[x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\]

Answer 21

are you instead solving by factoring or completing the square?

Answer 22

I guess you can't factor here, but you could complete the square.

Answer 23

ok i know the second equation you put

Answer 24

the quadratic formula. Okay, you've got
\[x^2+7x+5=0\]\[ax^2+bx+c=0\]Comparing the two, what are the needed values for \(a,b,c\) to make them equal?

Answer 25

zero

Answer 26

no...look at the two equations in my previous post. what value of \(a\) makes \(ax^2=x^2\)? what value of \(b\) makes \(bx=7x\)? what value of \(c\) makes \(c = 5\)?

Answer 27

by plugging in x^2 for ax^2 7x for bx and 5 for c and then i solve

Answer 28

i got c am i correct

Answer 29

@Nurali

Answer 30

Yes, C is the correct choice. the solutions are \[x = \frac{1}{2}(-7\pm\sqrt{29})\]

Answer 31

thanks for walking me thru this problem and being patient with me i am dumb when it comes to this stuff.