Question

Find the value of a, if the value -x² + 3x - a is equal to 8, when x = -1, is
(a) 12
(b) 14
(c) 15
(d) - 12
Explain... and Step-by-Step Explanation​

Answer 1

Answer:

a=-9+3x

Step-by-step explanation:

evaluate power

move expression to the right

add the numbers

change the signs

and final solution

I hope it can help (◍•ᴗ•◍)

Answer 2

Step-by-step explanation:

Given

$- {x}^{2} + 3x \: - a \: is \: equal \: to \: 8$

To Find

$value \: of \: a \: if \: equation \: - {x}^{2} + 3x - a \: is \: equal \: to \: 8 \: at \: x = - 1$

$\huge \ \underline {soulation}$

$- > - {x}^{2} + 3x - a = 8 \\ - > {( - 1)}^{2} + 3( - 1) - a = 8$

Concept:

When three is negative value and if it's power is even e.g, 2,4,6,8 then the resultant would come be a positive value. Similarly, if value is negative and its power is also -ve then resultant be a negative value.

=> plus minus = minus

$- > 1 - 3 - a = 8 \\ - > - 2 - a = 8$

Now,here 2 is in value-ve and when we shift it to right side it's sign gets changed from-ve to +ve

$- > - a = 8 + 2 = 10 \\ - > - a = 10 \\ a = - 10$

Check

$- > {( - 1)}^{2} + 3( - 1) - ( - 1) = 8 \\ - > 1 - 3 + 10 \\ - > - 2 + 10 = 8$