We can open the brackets and internal terms will multiply to other bracketed expression.
The product result of given expression is given by:
Option A: [tex]20t^2 + 9t - 20[/tex]
To find product result of [tex](5t - 4)(4t+ 5)[/tex]
We can open the bracket of first expression and do further internal multiplication as:
[tex]\begin{aligned}(5t - 4)(4t+ 5) &= 5t(4t+5) -4(4t+5)\\&= 5t \times 4t + 5t \times 5 - 4 \times 4t -4 \times 5\\&= 20t^2 + 25t -16t - 20\\&= 20t^2 + (25-16)t -20\text{\: (For like terms, coefficients combines)}\\&= 20t^2+ 9t - 20\end{aligned}[/tex]
(-4 times +5 is -20 since -1 times +1 is -1)
Thus, the product result is given by:
Option A: [tex]20t^2+ 9t - 20[/tex]
Learn more about algebraic multiplication here:
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