Question

Evaluate 4(2a – b) when a = –1 and b = 5.

Answer 1

Hey There!

Question:-

$\sf \longmapsto \: 4(2a - b)$

This is a algebraic expression. The values of a and b are given. The values are as follows :-

a = -1

And,

b = +5 .

Solution:-

$\sf \longmapsto4(2a - b)$

Note that a is multiplied with 2 that is :-

$\sf \longmapsto4(2 \times a \: - b)$

Now, Insert the values that is a = -1 and b = 5 :-

$\sf \longmapsto4(2 \times - 1 - 5)$

Here,we need to follow BODMAS Rule.

B = Brackets

O = Orders

D = Division

M = Multiplication

A = Addition

S = Subtraction

We need to solve the bracket's calculations first as it is the rule.

So, Firstly Multiply (2 × -1) :-

$\sf \longmapsto4( - 2 - 5)$

Note that, (-) × (-) equals to (+).

So, it will be 5+2,But as 5 is bigger number than 2, 5 contains a minus sign.So the result will be -7.

$\sf \longmapsto4( 5+ 2)$

On Simplification:-

$\sf \longmapsto4( - 7)$

$\sf \longmapsto4 \times (- 7)$

$\sf \longmapsto \: - 28$

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Henceforth the solution of the algebraic expression is :-

$\bf \:- 28$

Option B is correct!

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I hope this helps!

Please let me know if you have any questions.

~MisterBrian

Answer 2

4(2(-1)-5)
4(-2-5)
4(-7)
=-28 (B)