Question

[9.01] When the quadratic equation y = (x − 4)(2x + 5) is written in standard form, what is the value of the coefficient "b"? 2 3 −3 −20

Answer 1

expand (x − 4)(2x + 5) to get it in the form ax^2 + bx + c = 0

first multiply (2x + 5) by x then by -4 and simplify

Answer 2

thank you but i dont understand how u expand it

Answer 3

* in the form
y = ax^2 + bx + c

Answer 4

oh i think i undersatnd now the answer i got was -3 is that right?

Answer 5

first multiply 2x + 5 by x:
= x*2x + x*5 = 2x^2 + 5x

then by -4:-
= -4*2x +(-4*5)
can you finish this part?

Answer 6

first multiply 2x + 5 by x:
= x*2x + x*5 = 2x^2 + 5x

then by -4:-
= -4*2x +(-4*5)
can you finish this part?

Answer 7

(8x+-20)?

Answer 8

nevermind i did it wrong .. lemme start over

Answer 9

2x^2+5x then what happens after?

Answer 10

how do you get the: then by -4:-
= -4*2x +(-4*5)
can you finish this part? i dont understand that

Answer 11

you had the signs wrong in second part - time + -
so it should be -8x - 20

Answer 12

you had the signs wrong in second part - time + -
so it should be -8x - 20

Answer 13

oh i see then what comes after?

Answer 14

ok so now you have
2x^2 + 5x - 8x - 20

now you can add the 2 middle terms terms + 5x - 8x = -3x

so it simplifies to

y = 2x^2 - 3x - 20

so now you have the coefficients a b and c

Answer 15

ohhh! i get it now and "b" is -3! thank u so much :D that helped alot

Answer 16

welcome