## marmar3000 3 years ago Simplify (4x − 5)^2.

1. FaisalAyaz

(a+b)^2=a^2 + b^2 + 2ab

2. satellite73

does that mean "multiply"? start with $(4x+5)(4x+5)$ and do four multiplications

3. FaisalAyaz

(a-b)^2 = a^2 + b^2 -2ab

4. satellite73

oops rather $(4x-5)(4x-5)$

5. marmar3000

thankss(:

6. satellite73

do four multiplications, combine like terms, and then tell your teacher (gently) that there is nothing "simpler" about your result than there is in $$(4x-5)^2$$

7. marmar3000

is it 16x+25?

8. satellite73

oh no! careful here

9. satellite73

four multiplications i will write them out

10. satellite73

$(4x-5)(4x-5)=4x\times 4x-5\times 4x-5\times 4x+5\times 5$

11. FaisalAyaz

(4x-5)^2 = 16x^2 -40x +25.

12. marmar3000

16x-40x+25?

13. satellite73

then $$4x\times 4x=16x^2$$ $$-5\times 4x-5\times 4x=-20x-20x=-40x$$ $$(-5)\times (-5)=25$$ final answer is $16x^2-40x+25$

14. FaisalAyaz

now factorize it or solve by formula $x=-b \pm \sqrt{b^{2}-4ac}/2a$

15. FaisalAyaz

no marmar it's 16x^2 - 40x +25. not 16x

16. FaisalAyaz

now use quadratic formula or apply factorization method.it's up to u

17. FaisalAyaz

U got it marmar? just use formula (a-b)^2 = a^2 + b^2 -2ab. then find x by factorization or quadratic formula.Simple!

18. marmar3000

yea, thanks guys!