another problem?

Question

this is easy but i keep getting it wrong! please help me:( the book says the answer is 7/16 i cant get that answer. here's the problem: a(squared)-b(a-b).let a = -1/2 and b=1/4

Answer 1

The answer is 7/16. Be careful with your signs:

1/4 - 1/4(-1/2-1/4)

=1/4 - 1/4(-3/4)

=1/4 + 3/16

=7/16

Answer 2

hi ellen,

the trick here is to watch your signs and your order of operations as you substitute your values into the equation...you're correct it is an easy problem so here it goes

the equation is a^2 - b(a-b)

so putting in the values we get

(-1/2)^2 - (1/4)(-1/2 - (1/4))

ok dealing with the brackets first we get
(-1/2)^2 - (1/4)(-1/2 -1/4), we need to get a common denominator and do the operation inside the brackets, in this case the common denominator is 4 which gives us...

(-1/2)^2 - (1/4)(-2/4 - 1/4) then we simplify our brackets to give us

(-1/2)^2 - (1/4)(-3/4)

looking at the a^2 term that simplifies to
1/4 - (1/4)(-3/4)

doing the multiplication now we get
1/4 - (-3/16)

distribute the '-' through -3/16 and it becomes
1/4 + 3/16

we need another common denominator , in this case 16, and the expression becomes

(1/4)*(4/4) = 4/16 => 4/16+3/16

= 7/16

Hope this helps.

Answer 3

= (-1/2)^2 - 1/4(-1/2-1/4)
= 1/4 -1/4(-2/4-1/4)
= 1/4 - 1/4(-3/4)
= 1/4 + 3/16
= 4/16 +3/16
= 7/16

Answer 4

let see

(-1/2)^2 -(1/4)(-1/2-1/4)
= (1/4)-(1/4)(-3/4)
= 1/4+3/16=4/16+3/16
= 7/16

there is your answer