Question

Evaluate the following:
${(7x-2y)}^2$
${(3x+7y)}^2$

Answer 1

(a) ${\left(7x-2y\right)}^2={\left(7x\right)}^2+{\left(2y\right)}^2-2\times 7x\times 2y$ (${\left(a-b\right)}^2=a^2+b^2-2ab$)

$=49x^2-28xy+4y^2$

(b) ${\left(3x+7y\right)}^2={\left(3x\right)}^2+{\left(7y\right)}^2+2\times 3x\times 7y$ (${\left(a+b\right)}^2=a^2+b^2+2ab$)

$=9x^2+42xy+49y^2$