By the end of this lesson you will:
Kitchen: 5 kg of posho at shs/kg.
Rule: Write the substituted value in brackets every time.
If :
The brackets seem unnecessary now — they become essential with negatives.
From algebra-01: . Given m, m:
Steps: Label → substitute in brackets → compute
Write , before substituting.
Evaluate each expression. Show your working line by line.
Write each substituted form with brackets before computing.
Kitchen adds a delivery fee: total cost = (where = bags of posho).
Does order of computation matter?
Quick recall:
Write your answer before turning the page.
Is it:
Commit to one answer now.
With :
The exponent applies only to what it is directly attached to.
If , evaluate .
Show every working line.
Kitchen discount: net cost per kg = .
Now a subsidy makes (a negative value).
The bracket habit you built now shields your signs.
Without brackets: ✗ — wrong sign, wrong answer
Always write the negative value inside brackets at the moment of substitution.
The expression is . The value is .
Is :
Write your answer before the next slide.
Brackets decide what is squared.
(posho), (beans). Evaluate :
Kitchen floor — m, m:
Circular well — m:
Substitution's second job: verify that a value solves an equation.
Does satisfy ?
An expression is a machine: put in a value, get a number back.
Four rules: